The following chart compares various climate parameters
for cold ENSO episodes that have occurred since 1949. Except where noted the cold
episodes listed are those specified in the CPC's tabulation of Cold & Warm Episodes
by Season. The cold and warm episodes are based on the Oceanic Niño Index (ONI), which
is calculated using the three month running mean of ERSST.v5 SST anomalies in the
Niño 3.4 region with multiple-centered 30 year base periods. A description of the
parameters follows the chart. With the exception of years prior to 1957, a Nov-Mar
GWO phase space plot is included for each episode. Data for 2017-18 will be updated
periodically.

Year

ERSST
Version

Nov-Mar
AAM

Peak MEI4

Peak MEI Season

Peak
ONI

Peak ONI Season

L.A. Rain

GWO
Phase Plot

1949-501,2

v5

--

-1.445

APRMAY

-1.5

DJF

9.94

--

1950-511,3

v4

--

-1.235

NOVDEC

-0.8

NDJ, DJF

8.21

--

1954-551

v5

--

-1.528

MAYJUN (54)

-0.9

ASO

11.94

--

1955-561

v5

--

-2.209

MAYJUN (55)

-1.7

OND

16.00

--

1956-571

v3b

--

-1.490

MAYJUN (56)

-0.4

Several

9.54

--

1961-62

v2

-0.515

-1.065

DECJAN

-0.3

ASO, SON

18.79

1962-63

v3b

-1.264

-0.837

JANFEB

-0.4

OND, NDJ

8.38

1964-65

v5

-1.150

-1.476

JULAUG

-0.8

ASO - DJF

13.69

1967-683

v4

-0.773

-1.106

APRMAY

-0.7

JFM

16.58

1970-71

v5

-0.980

-1.870

MARAPR

-1.4

DJF, JFM

12.32

1971-72

v5

-0.174

-1.439

AUGSEP

-1.0

OND

7.17

1973-74

v5

-1.336

-1.912

DECJAN

-2.0

NDJ

14.92

1974-75

v5

-0.846

-1.230

OCTNOV

-0.8

OND

14.35

1975-76

v5

-0.716

-1.968

SEPOCT

-1.7

OND, NDJ

7.22

1983-84

v5

-1.099

-0.509

JANFEB

-1.0

OND

10.43

1984-85

v5

-0.600

-0.715

APRMAY

-1.1

NDJ

12.82

1988-89

v5

-1.144

-1.501

AUGSEP

-1.8

OND, NDJ

8.08

1995-96

v5

-0.227

-0.597

DECJAN

-1.0

SON - NDJ

12.46

1998-99

v5

-0.544

-1.123

JANFEB

-1.6

NDJ, DJF

9.09

1999-00

v5

-0.784

-1.189

JANFEB

-1.7

NDJ, DJF

11.57

2000-01

v5

-0.801

-.701

OCTNOV

-0.7

OND - DJF

17.94

2005-06

v5

-0.616

-0.575

MARAPR

-0.8

NDJ, DJF

13.19

2007-08

v5

-1.015

-1.579

FEBMAR

-1.6

NDJ - DJF

13.53

2008-09

v5

-0.599

-.723

FEBMAR

-0.8

DJF

9.08

2010-11

v5

-0.598

-1.888

AUGSEP

-1.7

SON, OND

20.20

2011-12

v5

-0.371

-0.980

DECJAN

-1.1

SON, OND

8.69

2016-17

v5

0.088

-0.363

SEPOCT

-0.7

ASO - OND

19.00

2017-185

v5

-0.550

-0.731

JANFEB

-1.0

NDJ

4.68

1. AAM and AAM tendency anomaly data not available.
2. Based on ONI values beginning with DJF 1949-50.
3. ONI did not meet threshold of 5 consecutive overlapping seasons using ERSST v5.
4. MEI values are normalized and may change as new data is added. Specified values
were current as of March 6, 2018.
5. Data as of March 31, 2018.

ERSST Version: The most recent ERSST version for which the
episode was designated a cold episode. (See Peak ONI below.)

Nov-Mar AAM: The mean of the global relative atmospheric angular
momentum anomaly for the period November 1 to March 31 of the following year. GWO
phase space data is calculated using code from the Global
Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann
and Berry, 2008.

Following is a chart comparing the 2015-16 El Nino to
warm ENSO episodes that have occurred since 1950. The warm episodes are based on the
revised Oceanic Niño Index (ONI) which is calculated using the three month running
mean of ERSST.v4 SST anomalies in the Niño 3.4 region with multiple-centered 30 year
base periods. Unless noted the warm episodes are those specified in the CPC's tabulation
of Cold & Warm Episodes by Season. A description of the parameters follows the
chart. With the exception of years prior to 1957, a Nov-Mar GWO phase space plot is
included for each warm episode.

Year

Jul-Sep
AAM

Nov-Mar
AAM

Peak MEI

Peak MEI Season

Peak
ONI

Peak ONI Season

L.A. Rain

GWO
Phase Plot

1951-521

--

--

0.822

JULAUG

0.9

SON

26.21

--

1952-532

--

--

0.788

APRMAY

0.7

FMA-AMJ

9.46

--

1953-542

--

--

0.484

AUGSEP

0.8

ASO, SON, OND

11.99

--

1957-583

--

0.773

1.474

DECJAN, JANFEB

1.7

DJF

21.13

1958-59

-0.919

-0.206

0.788

JANFEB

0.6

NDJ, DJF, JFM

5.58

1963-64

0.005

0.046

0.867

OCTNOV, DECJAN

1.2

SON, OND

7.93

1965-66

-0.826

-0.748

1.436

JULAUG

1.8

OND

20.44

1968-69

0.130

0.513

0.844

JANFEB

1.0

JFM

27.47

1969-70

0.358

0.413

0.670

OCTNOV

0.8

ASO, SON, OND

7.77

1972-73

-0.096

-0.239

1.827

JUNJUL, JULAUG

2.0

OND

21.26

1976-77

0.284

-0.828

1.029

AUGSEP

0.8

OND,NDJ

12.31

1977-78

-0.646

1.008

0.993

SEPOCT, OCTNOV

0.8

OND, NDJ

33.44

1979-804

0.496

-0.013

0.996

NOVDEC

0.6

NDJ, DJF

26.98

1982-83

0.938

2.337

3.011

FEBMAR

2.1

OND,NDJ, DJF

31.25

1986-875

0.232

0.019

2.140

APRMAY87

1.2

JFM

7.66

1987-885

1.153

1.000

1.982

JULAUG

1.6

JAS, ASO

12.48

1991-92

-0.008

0.808

2.269

MARAPR

1.6

DJF

21.00

1994-95

-0.422

0.764

1.419

SEPOCT

1.0

NDJ

24.35

1997-98

1.811

1.481

3.049

JULAUG,AUGSEP

2.3

OND, NDJ

31.01

2002-03

0.047

0.324

1.199

DECJAN

1.3

OND

16.49

2004-05

-0.020

0.747

1.055

FEBMAR

0.7

JAS-NDJ

37.25

2006-07

0.143

-0.322

1.322

OCTNOV

1.0

NDJ

3.21

2009-10

-0.103

0.303

1.521

JANFEB

1.3

NDJ,DJF

16.36

2014-156

-0.526

-0.297

0.997, 1.567

MAYJUN14, APRMAY15

0.6

OND, NDJ

8.52

2015-167

1.313

1.637

2.527

AUGSEP

2.3

NDJ

9.36

1. AAM and AAM tendency anomaly data for 1951-52 not available.
2. Continuous warm episode from DJF 1952/53 to DJF 1954.
3. AAM anomaly is average for Jan-Mar 1958.
4. Warm episode per ERSST.v4, but not ERSST.v3b.
5. Continuous warm episode from ASO 1986 to JFM 1988.
6. Warm episode per ERSST.v3b, but not ERSST.v4.
7. Data as of April 3, 2016.

Jul-Sep AAM & Nov-Mar AAM: The mean of the global relative atmospheric
angular momentum anomaly for the periods July 1 to September 30 amd November 1 to
March 31 of the following year. GWO phase space data is calculated using code from
the Global
Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann
and Berry, 2008.

Downtown Los Angeles (USC) ended the 2014-2015 rainfall
year (July 1 - June 30) with 8.52 inches of rain; well below the normal of 14.93 inches.
It was the fourth consecutive year of below normal rainfall in Los Angeles and much
of Southern California.

Constructive interference of the El Nino base state by
the active phase of the MJO resulted in negative 200-hPa velocity potential anomalies
and enhanced convection in the Eastern Pacific during the first half of July. This
appears to have contributed to the rapid development of Dolores from a tropical depression
on July 11 into a Category 4 hurricane July 15. Anomalously warm SSTs in the tropical
and sub-tropical Eastern Pacific also played a role, helping to maintain the strength
of Dolores and increasing the amount of water vapor entrained by the system and transported
into Southern California.

Many stations set
new records, not only for the date, but for any day in July. Downtown Los Angeles
(USC) set rainfall records for the date on Saturday and Sunday and tied Monday's record.
Downtown Los Angeles recorded 0.36 inch of rain Saturday. This is more rain than any
day in any July since recordkeeping began in 1877. That one day of rainfall even broke
the monthly record for July in Los Angeles! Prior to this event the wettest July on
record was in 1886, when 0.24 inch was recorded.

Though the rain created its own problems -- including
flash floods, debris flows and rock slides -- the soaking rains helped quell the Pines
Fire near Wrightwood and the North Fire near Cajon Pass. Over the three day period
from Saturday to Monday the Big Pines Remote Automated Weather Station (RAWS), near
the Pines Fire, recorded 3.12 inches of rain. Several stations in the San Gabriels
recorded more than three inches of rain, including Clear Creek and Opids Camp. Here's
a NWS compilation of some rainfall totals in the Los
Angeles forecast area and the San
Diego forecast area.

After dawdling around for several months our on again,
off again El Nino is finally
firing on all cyclinders and could reach ONI and MEI levels not seen since 1997-98
and 1982-83. The Multivariate
ENSO Index (MEI) for May-June was 2.06. This was the third highest value for the
season, exceeded only in 1983 (2.2) and 1997 (2.3). It is the second highest for the
season during the development phase of an El Nino event. The 2015 April-May-June Oceanic
Nino Index (ONI) value of 0.9 was higher than than in 1982 (0.6) and 1997 (0.6).
Several dynamical models in the IRI/CPC
ENSO Predictions Plume of forecast Nino 3.4 SST anomaly, released July 16, project
Nino 3.4 SST anomalies in excess of 2.5°C this fall.

Analysis of correlations of CMAP Precipitation with globally
integrated atmospheric angular momentum using ESRL/PSD's Linear
Correlations in Atmospheric Seasonal/Monthly Averages tool suggests that precipitation
in the southern half of California is more strongly correlated with atmospheric angular
momentum (AAM) than with Nino 3.4 SST. For example, compare the correlation of CMAP
Precipitation to AAM and
to Nino
3.4 SST for Dec-Jan-Feb 1980-2012. Cyclical increases in relative atmospheric
angular momentum are often associated with El Ninos. This can be seen in the plots
of the Global Wind Oscillation in my El
Nino Comparison Chart.

After being negative for 3 1/2 years, the PDO
Index has been positive since January 2014. December's PDO value of 2.51 was the
highest for that month on record since 1900. June's value of 1.54 was the 13th highest
since 1900.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Fourth Year of Below Average Rainfall for Los Angeles. Southern California Begins Rain Year with Record-Setting July Storm. El Nino Finally Firing On All Cylinders. PDO Index Remains Positive.http://www.sierraphotography.com/wxnotes/PermaLink,guid,400e0eae-c039-4ce7-8318-db9b2671d82f.aspxhttp://www.sierraphotography.com/wxnotes/FourthYearOfBelowAverageRainfallForLosAngelesSouthernCaliforniaBeginsRainYearWithRecordSettingJulyStormElNinoFinallyFiringOnAllCylindersPDOIndexRemainsPositive.aspx
Tue, 28 Jul 2015 15:07:55 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="NRL GOES E/W Composite VIS/IR (Day/Night) from Saturday, July 18, 2015 5:00 PM PDT with remnants of Hurricane Dolores off the coast of Baja. The remnants of Tropical Storm Enrique are farther to the west." href="wxdata1516/20150719.0000.goes_15.visir.bckgr_d.jpg" rel="wximage"> <img border="0" alt="NRL GOES E/W Composite VIS/IR (Day/Night) - Saturday, July 18, 2015 5:00 PM PDT" src="wxdata1516/20150719.0000.goes_15.visir.bckgr_c.jpg" width="300" height="220" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">NRL GOES E/W Composite VIS/IR (Day/Night)<br />
Post-tropical remnant low Dolores is west of Baja<br />
Saturday, July 18, 2015 5:00 PM PDT. </span>
</p>
</div>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) ended the 2014-2015 rainfall
year (July 1 - June 30) with 8.52 inches of rain; well below the normal of 14.93 inches.
It was the fourth consecutive year of below normal rainfall in Los Angeles and much
of Southern California.
</p>
<p>
<span class="dropcap">T</span>o kick off the new new rainfall year two waves of moisture
and instability associated with <a href="wxdata1516/20150719.0000.goes15.vapor.x.pacus.x.jpg" rel="wximage" target="_blank">ex-hurricane
Dolores, other tropical sources, and a strong monsoonal flow from Baja</a> resulted
in record-setting rainfall in Southern California from Saturday July 18 to Monday
July 20.
</p>
<p>
<span class="dropcap">C</span>onstructive interference of the El Nino base state by
the active phase of the MJO resulted in negative 200-hPa velocity potential anomalies
and enhanced convection in the Eastern Pacific during the first half of July. This
appears to have contributed to the rapid development of Dolores from a tropical depression
on July 11 into a Category 4 hurricane July 15. Anomalously warm SSTs in the tropical
and sub-tropical Eastern Pacific also played a role, helping to maintain the strength
of Dolores and increasing the amount of water vapor entrained by the system and transported
into Southern California.
</p>
<p>
<span class="dropcap">M</span>any stations <a href="wxdata1516/RERLOX072015_0541PDT.pdf" target="_blank">set
new records</a>, not only for the date, but for any day in July. Downtown Los Angeles
(USC) set rainfall records for the date on Saturday and Sunday and tied Monday's record.
Downtown Los Angeles recorded 0.36 inch of rain Saturday. This is more rain than any
day in any July since recordkeeping began in 1877. That one day of rainfall even broke
the monthly record for July in Los Angeles! Prior to this event the wettest July on
record was in 1886, when 0.24 inch was recorded.
</p>
<p>
<span class="dropcap">T</span>here was <a href="wxdata1516/UCAR_NEXRAD_KSOX_072015_0100zb.png" rel="wximage" target="_blank">very
heavy rain in the mountains on Sunday</a>, with rain rates exceeding an inch a hour.
From 5:15 p.m. to 5:25 p.m. a <a href="http://www.wunderground.com/personal-weather-station/dashboard?ID=KCAMOUNT12#history" target="_blank">CBS
Radio weather station on Mt. Wilson</a> recorded a half-inch of rain in just 10 minutes!
</p>
<p>
<span class="dropcap">T</span>hough the rain created its own problems -- including
flash floods, debris flows and rock slides -- the soaking rains helped quell the Pines
Fire near Wrightwood and the North Fire near Cajon Pass. Over the three day period
from Saturday to Monday the Big Pines Remote Automated Weather Station (RAWS), near
the Pines Fire, recorded 3.12 inches of rain. Several stations in the San Gabriels
recorded more than three inches of rain, including Clear Creek and Opids Camp. Here's
a NWS compilation of some rainfall totals in the <a href="wxdata1516/RRMLOX072015_1757PDT.pdf" target="_blank">Los
Angeles forecast area</a> and the <a href="wxdata1516/RRMSGX071915_1930PDT.pdf" target="_blank">San
Diego forecast area</a>.
</p>
<p>
<span class="dropcap">A</span>fter dawdling around for several months our on again,
off again El Nino is <a href="wxdata1516/sst_wind_anom_5day_ps32_072715b.gif" rel="wximage" target="_blank">finally
firing on all cyclinders</a> and could reach ONI and MEI levels not seen since 1997-98
and 1982-83. The <a href="http://www.esrl.noaa.gov/psd/enso/mei/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) for May-June was 2.06. This was the third highest value for the
season, exceeded only in 1983 (2.2) and 1997 (2.3). It is the second highest for the
season during the development phase of an El Nino event. The 2015 April-May-June <a href="http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml" target="_blank">Oceanic
Nino Index</a> (ONI) value of 0.9 was higher than than in 1982 (0.6) and 1997 (0.6).
Several dynamical models in the <a href="wxdata1516/IRI-CPC_ENSOPlume071615b.gif" rel="wximage" target="_blank">IRI/CPC
ENSO Predictions Plume of forecast Nino 3.4 SST anomaly</a>, released July 16, project
Nino 3.4 SST anomalies in excess of 2.5°C this fall.
</p>
<p>
<span class="dropcap">A</span>nalysis of correlations of CMAP Precipitation with globally
integrated atmospheric angular momentum using ESRL/PSD's <a href="http://www.esrl.noaa.gov/psd/data/correlation/" target="_blank">Linear
Correlations in Atmospheric Seasonal/Monthly Averages tool</a> suggests that precipitation
in the southern half of California is more strongly correlated with atmospheric angular
momentum (AAM) than with Nino 3.4 SST. For example, compare the correlation of CMAP
Precipitation to <a href="wxdata1516/CorrDecFeb1980_2012_Precip_AAMb.gif" rel="wximage" target="_blank">AAM</a> and
to <a href="wxdata1516/CorrDecFeb1980_2012_Precip_Nino34b.gif" rel="wximage" target="_blank">Nino
3.4 SST</a> for Dec-Jan-Feb 1980-2012. Cyclical increases in relative atmospheric
angular momentum are often associated with El Ninos. This can be seen in the plots
of the Global Wind Oscillation in my <a href="http://www.sierraphotography.com/wxnotes/ElNinoComparisonChartFor20142015.aspx" target="_blank">El
Nino Comparison Chart</a>.
</p>
<p>
<span class="dropcap">A</span>fter being negative for 3 1/2 years, the <a href="http://jisao.washington.edu/pdo/" target="_blank">PDO
Index</a> has been positive since January 2014. December's PDO value of 2.51 was the
highest for that month on record since 1900. June's value of 1.54 was the 13th highest
since 1900.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<p>
</p>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=400e0eae-c039-4ce7-8318-db9b2671d82f" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl Ninoflash floodGlobal Wind Oscillation (GWO)Los Angeles rainfallMadden-Julian Oscillation (MJO)Multivariate ENSO Index (MEI)record rainfallweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=7d519dab-e8b2-4314-92d7-56c7789bd70bhttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,7d519dab-e8b2-4314-92d7-56c7789bd70b.aspxGary Valle

Following is a chart comparing 2014-15 to warm ENSO episodes
that have occurred since 1950. The warm episodes are based on the revised Oceanic
Niño Index (ONI) which is calculated using the three month running mean of ERSST.v4
SST anomalies in the Niño 3.4 region with multiple-centered 30 year base periods.
Unless noted the warm episodes are those specified in the CPC's tabulation of Cold
& Warm Episodes by Season. A description of the parameters follows the chart.
With the exception of years prior to 1957, a GWO phase space plot is included for
each warm episode.

Jul-Sep AAM & Nov-Mar AAM: The mean of the global relative atmospheric
angular momentum anomaly for the periods July 1 to September 30 amd November 1 to
March 31 of the following year. Data is from the GWO phase space data file linked
on the Global
Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann
and Berry, 2008.

Current Departure from Normal Precipitation Since October
1
AHPS Precpitation Analysis as of 1/19/2015 12:00 UTC.

After being negative for 3 1/2 years, the PDO
Index has been positive since January 2014. December's PDO value of 2.51 is the
highest for that month on record (since 1900), exceeding December 2002's value of
2.10 and December 1940's value of 1.96.

Even so, the highly anticipated 2014-15 El Nino continues
to dawdle with little ocean-atmosphere coupling and an emphasis on an higher amplitude
meridional flows. Due in part to the upwelling phase of a series of oceanic Kelvin
waves, equatorial Pacific heat content and SST anomalies have diminished. After having
been at or above 0.5 °C for the past twelve weeks OISST.v2
Nino 3.4 SST Anomalies dropped to 0.4 °C for the week centered on January 7, 2015
and as of the week of January 14 was at 0.5 °C.

So far this rain season Northern California and the coastal
areas of Central and Southern California have fared much better in terms of precipitation
than last year. As of today Downtown Los Angeles (USC) precipitation for the water
year (beginning July 1) is at 90% of normal and Downtown San Francisco is at 127%.

At the moment it doesn't look like the snowpack will
get much help in the short term. After fending off a little shortwave the blocking
ridge is forecast to rebuild to new heights, bringing unseasonably mild weather to
much of the West Coast. There does appear to be the possibility of a wildcard low
latitude low developing under the block and that could result in some precipitation
in Southern California next week. If such a system develops, given the warm state
of the Eastern Pacific, it could be wetter than expected. We'll see!

In the early morning hours of Friday, December 12, 2014,
a very strong cold front, enhanced with moisture from an atmospheric river, produced
a line of strong storms that produced rain rates in the Springs Fire burn area as
high as 2 inches per hour. This resulted in widespread flash floods and debris flows
in the burn area, much of which is in Pt. Mugu State Park. Mud and debris flows originating
from the burn area inundated homes below Conejo Mountain and closed Pacific Coast
Highway. This slideshow
includes photos of the aftermath of the flash floods and debris flows in Blue
Canyon, Sycamore Canyon and Upper Sycamore. The photos were taken on a trail run on
December 14, 2014. Also included are some NWS Los Angeles/Oxnard tweets and some additional
meteorological images and info.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
PDO Index the Highest on Record for December. El Nino Continues to Dawdle. Coastal California vs Sierra Precipitation. Pt. Mugu State Park Flash Floods & Debris Flows.http://www.sierraphotography.com/wxnotes/PermaLink,guid,7728b83e-4978-41c4-98d7-4ffd907553ca.aspxhttp://www.sierraphotography.com/wxnotes/PDOIndexTheHighestOnRecordForDecemberElNinoContinuesToDawdleCoastalCaliforniaVsSierraPrecipitationPtMuguStateParkFlashFloodsDebrisFlows.aspx
Tue, 20 Jan 2015 16:44:31 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="Southwestern U.S. Current Departure from Normal Precipitation Since October 1 as of 1/19/2015 12:00 UTC." href="wxdata1415/WY_Oct1_Precip_Depart_011915_12zb.png" rel="wximage"> <img border="0" alt="Southwestern U.S. Current Departure from Normal Precipitation Since October 1 as of 1/19/2015 12:00 UTC." src="wxdata1415/WY_Oct1_Precip_Depart_011915_12zc.png" width="350" height="215" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">Current Departure from Normal Precipitation Since October
1<br />
AHPS Precpitation Analysis as of 1/19/2015 12:00 UTC. </span>
</p>
</div>
<p>
<span class="dropcap">A</span>fter being negative for 3 1/2 years, the <a href="http://jisao.washington.edu/pdo/" target="_blank">PDO
Index</a> has been positive since January 2014. December's PDO value of 2.51 is the
highest for that month on record (since 1900), exceeding December 2002's value of
2.10 and December 1940's value of 1.96.
</p>
<p>
<span class="dropcap">E</span>ven so, the highly anticipated 2014-15 El Nino continues
to dawdle with little ocean-atmosphere coupling and an emphasis on an higher amplitude
meridional flows. Due in part to the upwelling phase of a series of oceanic Kelvin
waves, equatorial Pacific heat content and SST anomalies have diminished. After having
been at or above 0.5 °C for the past twelve weeks <a href="http://www.cpc.ncep.noaa.gov/data/indices/wksst8110.for" target="_blank">OISST.v2
Nino 3.4 SST Anomalies</a> dropped to 0.4 °C for the week centered on January 7, 2015
and as of the week of January 14 was at 0.5 °C.
</p>
<p>
<span class="dropcap">T</span>he <a href="http://www.esrl.noaa.gov/psd/enso/mei/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) for NOV/DEC has decreased 0.13 SD to +0.58, but has maintained
its historic rank (since 1950) at 47. A rank of 46 is the threshold for weak El Nino
conditions in the context of the MEI. The <a href="wxdata1415/psd_gwo_fnl_011915b.png" rel="wximage" target="_blank">FNL
Global Wind Oscillation for the past 90 days</a> continues to reflect the lack of
definitive atmospheric coupling.
</p>
<p>
<span class="dropcap">S</span>o far this rain season Northern California and the coastal
areas of Central and Southern California have fared much better in terms of precipitation
than last year. As of today Downtown Los Angeles (USC) precipitation for the water
year (beginning July 1) is at 90% of normal and Downtown San Francisco is at 127%.
</p>
<p>
<span class="dropcap">A</span>s this AHPS plot of <a href="wxdata1415/WY_Oct1_Precip_PON_011915_12zb.png" rel="wximage" target="_blank">precipitation
since October 1</a> shows, many areas of California have recorded at least 75% of
normal precipitation. Unfortunately the Sierra Nevada is not one of them. While better
than <a href="http://cdec.water.ca.gov/cgi-progs/reports/DLYSWEQ.20140120" target="_blank">last
year's dismal 14% of normal on this date</a>, this year's snowpack is currently well
below average, and was<a href="http://cdec.water.ca.gov/cgi-progs/reports/DLYSWEQ.20150115" target="_blank"> last
reported at 36%</a>. Here is an AHPS plot of <a href="wxdata1415/WY_Oct1_Precip_Depart_011915_12zb.png" rel="wximage" target="_blank">precipitation
departure since October 1</a> that shows the deficits in the Sierra Nevada.
</p>
<p>
<span class="dropcap">A</span>t the moment it doesn't look like the snowpack will
get much help in the short term. After fending off a little shortwave the blocking
ridge is forecast to rebuild to new heights, bringing unseasonably mild weather to
much of the West Coast. There does appear to be the possibility of a wildcard low
latitude low developing under the block and that could result in some precipitation
in Southern California next week. If such a system develops, given the warm state
of the Eastern Pacific, it could be wetter than expected. We'll see!
</p>
<p>
<span class="dropcap">I</span>n the early morning hours of Friday, December 12, 2014,
a very strong cold front, enhanced with moisture from an atmospheric river, produced
a line of strong storms that produced rain rates in the Springs Fire burn area as
high as 2 inches per hour. This resulted in widespread flash floods and debris flows
in the burn area, much of which is in Pt. Mugu State Park. Mud and debris flows originating
from the burn area inundated homes below Conejo Mountain and closed Pacific Coast
Highway. This <a href="http://www.photographyontherun.com/ssprun.asp?id=1305" target="_blank">slideshow
includes photos of the aftermath of the flash floods and debris flows</a> in Blue
Canyon, Sycamore Canyon and Upper Sycamore. The photos were taken on a trail run on
December 14, 2014. Also included are some NWS Los Angeles/Oxnard tweets and some additional
meteorological images and info.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<p>
</p>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=7728b83e-4978-41c4-98d7-4ffd907553ca" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)Los Angeles rainfallMultivariate ENSO Index (MEI)precipitation outlookSierra snowpackweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=d6efcb6a-0ca4-4210-bccf-e045770be27chttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,d6efcb6a-0ca4-4210-bccf-e045770be27c.aspxGary Valle

After being negative for 3 1/2 years, the PDO
Index has been positive since January 2014. October's PDO value of 1.49 is the
6th highest for that month since 1900 and comparable to PDO Index values in October
1997, 1957, 1993, and 1987.

A warm Pacific may have contributed to the amount of
precipitation produced in California by a large
Pacific upper level low this past week. Two periods of rain were observed in Southern
California -- one on Sunday and the other on Tuesday and Wednesday.

Even with the parent low lifting
to the north on Tuesday and the 570 mb contour near Santa Barbara, the very
moist southerly flow orographic lift and sufficient dynamics produced widespread
precipitation in Southern California with some impressive precipitation totals. Tuesday
record rainfall for the date occurred at both Downtown Los Angeles and Downtown San
Francisco. Yucaipa Ridge in the San Bernardino Mountains recorded a whopping three-day
rainfall total of 14.6 inches. Following are three-day rainfall compilations from
the NWS Los Angeles/Oxnard and NWS
San Diego.

Here are graphics from the CNRFC with gridded precipitation
totals for the four day period from early Sunday morning to early Thursday morning
for Southern
California, the Sierra
Nevada and the San
Francisco Bay Area. Some preliminary precipitation totals of 5 inches or more
are noted.

One thing is very clear; we have a lot to learn about
the atmosphere's response to anomalously warm equatorial Pacific SSTs. It's difficult
to imagine a better scenario for El Niño development than the conditions seen in the
equatorial Pacific earlier this year.

The Oceanic
Niño Index (ONI) jumped from -0.5 in the FMA season to -0.1 in MAM, and then to
+0.1 in AMJ. During that same period the Multivariate
ENSO Index (MEI) jumped from a rank of 35 in MARAPR to 59 in APRMAY -- a value
that put it on the doorstep of a strong El Nino ranking. Which all looked supportive
of at least a moderate El Nino developing.

But it didn't. After climbing up to 0.6 °C in late May, Nino
3.4 region SST anomalies dropped to below 0.0 °C in late July. Since then a more
modest downwelling Kelvin wave has restored some of the basin heat content and Nino
3.4 anomalies have rebounded back to 0.6 °C.

So what's next? While El Nino development still appears
to be possible this Winter, it would be one of the two latest developing El Ninos
in the record from 1950 to the present -- the other being 1952-53. One possibility
is that this year's vacillations are the precursor to the EARLY development of an
El Nino event next year.

The 1981-2010 climate normal average rainfall for Downtown
Los Angeles in November is 1.04 inches. Month to date we're about average for the
date, and water year to date we're ahead of last year, but about 0.6 inch below normal.

Based on the current GFS and ECMWF forecasts those deficits
are probably going to increase over the next two weeks, but it is way too early in
the rain season to attribute the dry weather to a continued dry pattern. El Niño or
not; dry November or not; the switch from a cold Pacific to a warm Pacific is a significant
change and one that some guidance suggests should increase our rainfall. We'll see!

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Another El Nino Near Miss? Fast-Moving Front and Trough Brings a Shot of Rain & Snow to California. Dry Rain Season Ahead for Southern California?http://www.sierraphotography.com/wxnotes/PermaLink,guid,1d92dc62-2cc3-493a-82d3-a91e6977756d.aspxhttp://www.sierraphotography.com/wxnotes/AnotherElNinoNearMissFastMovingFrontAndTroughBringsAShotOfRainSnowToCaliforniaDryRainSeasonAheadForSouthernCalifornia.aspx
Fri, 07 Nov 2014 22:18:36 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="SST NINO Region Anomalies from the CPC ENSO Diagnostic Discussion 11/6/2014." href="wxdata1415/cpc_ninoregionanom103014b.gif" rel="wximage"> <img border="0" alt="SST NINO Region Anomalies from the CPC ENSO Diagnostic Discussion 11/6/2014." src="wxdata1415/cpc_ninoregionanom103014c.jpg" width="300" height="374" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">SST NINO Region Anomalies<br />
From the CPC ENSO Diagnostic Discussion 11/6/2014. </span>
</p>
</div>
<p>
<span class="dropcap">O</span>ne thing is very clear; we have a lot to learn about
the atmosphere's response to anomalously warm equatorial Pacific SSTs. It's difficult
to imagine a better scenario for El Niño development than the conditions seen in the
equatorial Pacific earlier this year.
</p>
<p>
<span class="dropcap">A</span>fter being negative for 42 out of the previous 43 months,
the <a href="http://jisao.washington.edu/pdo/" target="_blank">Pacific Decadal Oscillation</a> (PDO)
index turned positive in January 2014 and has remained positive through the summer.
Beginning in January and ending in late June the downwelling phase of a <a href="wxdata1415/cpc_tlon_heatanom103014b.gif" rel="wximage" target="_blank">very
strong Kelvin wave</a> propagated across the Pacific, with <a title="From the CPC ENSO Diagnostic Discussion 11/6/2014." href="wxdata1415/cpc_heat-last-year103014b.gif" rel="wximage" target="_blank">upper
ocean area-averaged heat content anomaly</a> between 180 and 100W peaking at the end
of March. Since January there have been westerly wind bursts and <a href="wxdata1415/time_lon_EQ_hf_uwnd_uwnd_mean_anom_201211_201411_2014110709b.gif" rel="wximage" target="_blank">periods
of increased low-level westerly zonal wind anomalies</a> of variable duration and
extent.
</p>
<p>
<span class="dropcap">T</span>he <a href="http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml" target="_blank">Oceanic
Niño Index (ONI)</a> jumped from -0.5 in the FMA season to -0.1 in MAM, and then to
+0.1 in AMJ. During that same period the <a href="http://www.esrl.noaa.gov/psd/enso/mei/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) jumped from a rank of 35 in MARAPR to 59 in APRMAY -- a value
that put it on the doorstep of a strong El Nino ranking. Which all looked supportive
of at least a moderate El Nino developing.
</p>
<p>
<span class="dropcap">B</span>ut it didn't. After climbing up to 0.6 °C in late May, <a title="SST NINO Region Anomalies from the CPC ENSO Diagnostic Discussion 11/6/2014." href="wxdata1415/cpc_ninoregionanom103014b.gif" rel="wximage" target="_blank">Nino
3.4 region SST anomalies</a> dropped to below 0.0 °C in late July. Since then a more
modest downwelling Kelvin wave has restored some of the basin heat content and Nino
3.4 anomalies have rebounded back to 0.6 °C.
</p>
<p>
<span class="dropcap">S</span>o what's next? While El Nino development still appears
to be possible this Winter, it would be one of the two latest developing El Ninos
in the record from 1950 to the present -- the other being 1952-53. One possibility
is that this year's vacillations are the precursor to the EARLY development of an
El Nino event next year.
</p>
<p>
<span class="dropcap">O</span>ne worrisome detail is that the <a href="http://www.esrl.noaa.gov/psd/map/clim/test_maproom.html" target="_blank">Global
Wind Oscillation</a> (GWO) has been behaving similarly to the failed El Nino of 2012.
Compare this plot of the <a href="wxdata1415/gwo_060114_103114b.png" rel="wximage" target="_blank">GWO
from June 1 to October 31 of this year</a> to the plot of the <a href="wxdata1415/gwo_060112_103112b.png" rel="wximage" target="_blank">GWO
from June 1 to October 31, 2012</a>. In both 2014 and 2012 the GWO has shown a neutral
or weak La Nina-like response. The <a href="wxdata1415/gwo_060197_103197b.png" rel="wximage" target="_blank">GWO
for the period June 1 to October 31, 1997</a> is an example of a definitive atmospheric
response to strong El Nino conditions.
</p>
<p>
<span class="dropcap">O</span>n a more positive note, a <a href="wxdata1415/UCAR_NEXRAD_110114_0700zb.png" rel="wximage" target="_blank">relatively
strong</a>, but fast-moving <a href="wxdata1415/ramdis_gwir404_20141101070000b.gif" rel="wximage" target="_blank">Pacific
cold front and trough</a> resulted in <a href="wxdata1415/CNRFC_7Day_QPE_110714_12zb.jpg" rel="wximage" target="_blank">rain
and snow in California</a> over Halloween. In the Los Angeles area rainfall amounts
generally <a href="wxdata1415/CNRFC_Precip_raw_110114b.jpg" rel="wximage" target="_blank">varied
from around 0.3 inch to 0.75 inch</a> or so with isolated amounts as high as about
2.0 inches in the mountains. Here are some tabulated rainfall amounts from around
the area from the <a href="wxdata1415/RRMLOX110114_1905PST.pdf" target="_blank">NWS
Los Angeles/Oxnard</a> and <a href="wxdata1415/RRMSGX110214_1030PDT.pdf" target="_blank">NWS
San Diego</a>.
</p>
<p>
<span class="dropcap">T</span>he 1981-2010 climate normal average rainfall for Downtown
Los Angeles in November is 1.04 inches. Month to date we're about average for the
date, and water year to date we're ahead of last year, but about 0.6 inch below normal.
</p>
<p>
<span class="dropcap">B</span>ased on the current GFS and ECMWF forecasts those deficits
are probably going to increase over the next two weeks, but it is way too early in
the rain season to attribute the dry weather to a continued dry pattern. El Niño or
not; dry November or not; the switch from a cold Pacific to a warm Pacific is a significant
change and one that some guidance suggests should increase our rainfall. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<p>
</p>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=1d92dc62-2cc3-493a-82d3-a91e6977756d" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)Los Angeles rainfallMultivariate ENSO Index (MEI)precipitation outlookweatherWesterly Wind Burst (WWB)http://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=d3d30989-63e9-4c81-95ae-9bba8f08fbddhttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,d3d30989-63e9-4c81-95ae-9bba8f08fbdd.aspxGary Valle

Two-Year Percentage of Normal Precipitation
July 1, 2012 to June 30, 2014 (WRCC).

Downtown Los Angeles (USC) finished the water year (July
1 to June 30) with 6.08 inches of recorded rainfall. This is about 41% of the 1981-2010
normal of 14.93 inches. It was the seventh driest water year since recordkeeping began
in 1877. When combined with last year's water year total of 5.85 inches, the back-to-back
water years from July 1, 2012 to June 30, 2014 are the driest on record for Los Angeles.
The total rainfall deficit over the two year period was about 18 inches.

El Nino has been knocking on the door, but until very
recently the atmosphere has only been responding in spits and sputters.

The weekly OISST.v2
Nino 3.4 SST temperature anomaly has been vacillating in the range 0.4 to 0.6
beginning with the week centered on April 23, 2014 and now stands at 0.5. Nino 1+2
and Nino 3 anomalies have generally been increasing and as of the week centered on
June 25 are at 1.6 and 1.0 respectively. Here is a plot
of the Nino regions SST anomalies from the CPC. Following a period of strengthened
tradewinds, another westerly wind burst has developed in the Western Pacific. There
have been several
WWB this year and the most recent WWB could lead to additional warming of equatorial
SSTs.

The Global
Wind Oscillation (GWO) can be a useful tool for evaluating the degree to which
the atmosphere is responding to El Nino or La Nina conditions. As this plot of the GWO
for the period March 1 to July 31, 1997 shows, during the spring and summer of
1997 El Nino conditions were already resulting in a definitive atmospheric response.
Here is a plot of the GWO
from March 1 to July 1 of this year. Over most of this period the GWO has shown
a neutral or weak La Nina-like response. Recently the GWO has exhibited a positive
shift in AAM anomaly that, if sustained, could be indicative of a coupled ocean-atmosphere
response.

The Plume-based and Consensus Forecasts in the June
19 IRI/CPC ENSO Quick Look (PDF) show an increasing chance of El Nino conditions
developing over the NH summer, with an approximately 80% chance of El Nino conditions
being established by the OND season. A July
2 run of the CFSv2 forecasts Nino 3.4 anomalies to briefly decline, then increase
substantially from July into October. We'll see!

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Los Angeles Experiences Driest Back-to-Back Water Years On Record. Transition to Fully-Developed El Nino In Progress.http://www.sierraphotography.com/wxnotes/PermaLink,guid,d3d30989-63e9-4c81-95ae-9bba8f08fbdd.aspxhttp://www.sierraphotography.com/wxnotes/LosAngelesExperiencesDriestBacktoBackWaterYearsOnRecordTransitionToFullyDevelopedElNinoInProgress.aspx
Thu, 03 Jul 2014 20:48:36 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="Percentage of Normal Precipitation for July 1, 2012 to June 30, 2014 (WRCC)" href="wxdata1314/wrcc_precip_ponJul12012Jun302014b.gif" rel="wximage"> <img border="0" alt="Percentage of Normal Precipitation for July 1, 2012 to June 30, 2014 (WRCC)" src="wxdata1314/wrcc_precip_ponJul12012Jun302014c.jpg" width="300" height="232" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">Two-Year Percentage of Normal Precipitation<br />
July 1, 2012 to June 30, 2014 (WRCC). </span>
</p>
</div>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) finished the water year (July
1 to June 30) with 6.08 inches of recorded rainfall. This is about 41% of the 1981-2010
normal of 14.93 inches. It was the seventh driest water year since recordkeeping began
in 1877. When combined with last year's water year total of 5.85 inches, the back-to-back
water years from July 1, 2012 to June 30, 2014 are the driest on record for Los Angeles.
The total rainfall deficit over the two year period was about 18 inches.
</p>
<p>
<span class="dropcap">E</span>l Nino has been knocking on the door, but until very
recently the atmosphere has only been responding in spits and sputters.
</p>
<p>
<span class="dropcap">T</span>he weekly <a href="http://www.cpc.ncep.noaa.gov/data/indices/wksst8110.for" target="_blank">OISST.v2
Nino 3.4 SST temperature anomaly</a> has been vacillating in the range 0.4 to 0.6
beginning with the week centered on April 23, 2014 and now stands at 0.5. Nino 1+2
and Nino 3 anomalies have generally been increasing and as of the week centered on
June 25 are at 1.6 and 1.0 respectively. Here is a <a href="wxdata1314/CPC_ElNinoRegionSSTAnom063014.gif" rel="wximage" target="_blank">plot
of the Nino regions SST anomalies</a> from the CPC. Following a period of strengthened
tradewinds, another westerly wind burst has developed in the Western Pacific. There
have been <a href="wxdata1314/CPC_CDAS850a062914b.gif" rel="wximage" target="_blank">several
WWB this year</a> and the most recent WWB could lead to additional warming of equatorial
SSTs.
</p>
<p>
<span class="dropcap">I</span>n response to the <a href="wxdata1314/CPC_tlon_heat_062714b.gif" rel="wximage" target="_blank">upwelling
phase of an oceanic Kelvin wave</a> there has been a <a href="wxdata1314/CPC_EqHeatContentAnom063014.gif" rel="wximage" target="_blank">decrease
in subsurface Pacific equatorial heat content</a> and some <a href="wxdata1314/CPC_EqTempDepth_062714b.gif" rel="wximage" target="_blank">associated
cooling at depth</a>.
</p>
<p>
<span class="dropcap">T</span>he <a href="http://www.esrl.noaa.gov/psd/map/clim/test_maproom.html" target="_blank">Global
Wind Oscillation</a> (GWO) can be a useful tool for evaluating the degree to which
the atmosphere is responding to El Nino or La Nina conditions. As this plot of the <a href="wxdata1314/gwo_030197_073197b.png" rel="wximage" target="_blank">GWO
for the period March 1 to July 31, 1997</a> shows, during the spring and summer of
1997 El Nino conditions were already resulting in a definitive atmospheric response.
Here is a plot of the <a href="wxdata1314/gwo_030114_070114b.png" rel="wximage" target="_blank">GWO
from March 1 to July 1 of this year</a>. Over most of this period the GWO has shown
a neutral or weak La Nina-like response. Recently the GWO has exhibited a positive
shift in AAM anomaly that, if sustained, could be indicative of a coupled ocean-atmosphere
response.
</p>
<p>
<span class="dropcap">T</span>he Plume-based and Consensus Forecasts in the <a href="wxdata1314/IRI_CPC_Quick_Look061914.pdf" target="_blank">June
19 IRI/CPC ENSO Quick Look</a> (PDF) show an increasing chance of El Nino conditions
developing over the NH summer, with an approximately 80% chance of El Nino conditions
being established by the OND season. A <a href="wxdata1314/CFSv2Nino34Anom070214b.gif" rel="wximage" target="_blank">July
2 run of the CFSv2</a> forecasts Nino 3.4 anomalies to briefly decline, then increase
substantially from July into October. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<p>
</p>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=d3d30989-63e9-4c81-95ae-9bba8f08fbdd" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)Los Angeles rainfallWesterly Wind Burst (WWB)http://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=bef487c5-4159-40c7-98d4-02105bc42a0fhttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,bef487c5-4159-40c7-98d4-02105bc42a0f.aspxGary Valle

Downtown Los Angeles Rainfall
Driest Calendar Years 1878-2013.

Since January 1 Downtown Los Angeles has recorded only
3.60 inches of rain, making it the driest calendar year since recordkeeping began
in July of 1877. The previous record of 4.08 inches was set in 1953 and 1947. Downtown
Los Angeles averages about 15 inches of rain in a calendar year.

Precipitation composites for years with comparable PD0-AMO
indices constructed by Dr. Klaus Wolter of the Cooperative
Institute for Research in Environmental Sciences at the University of Colorado
appears to have anticipated this year's drought in Southern California. While Oct-Dec
anomalies for Southern California were -0.5 to -0.7 SD below the 1895-2000 Longterm
Average, Jan-Mar
anomalies were -0.1 to -0.3 SD below average. Assuming the anomaly maps to be
correlative the drought's stranglehold on Southern California may weaken somewhat
over the next three months.

To get an idea of how the precipitation anomaly might
vary over the next three months, the US Climate Division Dataset Mapping Page was
used to recreate the standardized Oct-Dec
precipitation anomaly and Jan-Mar
precipitation anomaly maps using the same years as Dr. Wolter's composites. Then
standardized composite precipitation anomaly maps were constructed for the months
of January, February,
and March.
Based on these composites some lessening of the severity of the drought in Southern
California is suggested throughout the period Jan-Mar with the biggest improvement
indicated in March -- except for coastal Southern California. A map showing the composite
precipitation anomaly in inches for the period October
to March was also generated.

While today's medium range forecasts and 6-10 day and
8-14 day precipitation outlooks aren't particularly encouraging there are some straws
to grasp. The AO
Index, which has been positive for most of the rainy season is now negative and
the Global Wind
Oscillation (GWO) is in its first full orbit into positive AAM territory in several
months. Whether these changes eventually result in rain for Southern California we'll
just have to see.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Driest Calendar Year in Los Angeles Since Recordkeeping Began in 1877. Composites Suggest Below Average Rainfall to Continue, But Some Lessening of the Drought in Southern California Possible.http://www.sierraphotography.com/wxnotes/PermaLink,guid,bef487c5-4159-40c7-98d4-02105bc42a0f.aspxhttp://www.sierraphotography.com/wxnotes/DriestCalendarYearInLosAngelesSinceRecordkeepingBeganIn1877CompositesSuggestBelowAverageRainfallToContinueButSomeLesseningOfTheDroughtInSouthernCaliforniaPossible.aspx
Wed, 01 Jan 2014 21:44:12 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="Downtown Los Angeles Rainfall for the Driest Calendar Years from 1878-2013." href="wxdata1314/LA_DriestCY1878_2013b.png" rel="wximage"> <img border="0" alt="Downtown Los Angeles Rainfall for the Driest Calendar Years from 1878-2013." src="wxdata1314/LA_DriestCY1878_2013c.png" width="300" height="202" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">Downtown Los Angeles Rainfall<br />
Driest Calendar Years 1878-2013.<br />
</span>
</p>
</div>
<p>
<span class="dropcap">S</span>ince January 1 Downtown Los Angeles has recorded only
3.60 inches of rain, making it the driest calendar year since recordkeeping began
in July of 1877. The previous record of 4.08 inches was set in 1953 and 1947. Downtown
Los Angeles averages about 15 inches of rain in a calendar year.
</p>
<p>
<span class="dropcap">P</span>recipitation composites for years with comparable PD0-AMO
indices constructed by Dr. Klaus Wolter of the <a href="http://cires.colorado.edu/index.html" target="_blank">Cooperative
Institute for Research in Environmental Sciences</a> at the University of Colorado
appears to have anticipated this year's drought in Southern California. While <a title="Prepared by Klaus Wolter, CIRES &amp; NOAA-ESRL PSD" href="wxdata1314/Wolter_PrecipCompOctDecPDOAMO2014b.jpg" rel="wximage" target="_blank">Oct-Dec
anomalies</a> for Southern California were -0.5 to -0.7 SD below the 1895-2000 Longterm
Average, <a title="Prepared by Klaus Wolter, CIRES &amp; NOAA-ESRL PSD" href="wxdata1314/Wolter_PrecipCompJanMarPDOAMO2014b.jpg" rel="wximage" target="_blank">Jan-Mar
anomalies</a> were -0.1 to -0.3 SD below average. Assuming the anomaly maps to be
correlative the drought's stranglehold on Southern California may weaken somewhat
over the next three months.
</p>
<p>
<span class="dropcap">T</span>o get an idea of how the precipitation anomaly might
vary over the next three months, the US Climate Division Dataset Mapping Page was
used to recreate the standardized <a href="wxdata1314/AfterWolter_PrecipCompOctDecPDOAMO2014b.png" rel="wximage" target="_blank">Oct-Dec
precipitation anomaly</a> and <a href="wxdata1314/AfterWolter_PrecipCompJanMarPDOAMO2014b.png" rel="wximage" target="_blank">Jan-Mar
precipitation anomaly</a> maps using the same years as Dr. Wolter's composites. Then
standardized composite precipitation anomaly maps were constructed for the months
of <a href="wxdata1314/AfterWolter_PrecipCompJanPDOAMO2014b.png" rel="wximage" target="_blank">January</a>, <a href="wxdata1314/AfterWolter_PrecipCompFebPDOAMO2014b.png" rel="wximage" target="_blank">February</a>,
and <a href="wxdata1314/AfterWolter_PrecipCompMarPDOAMO2014b.png" rel="wximage" target="_blank">March</a>.
Based on these composites some lessening of the severity of the drought in Southern
California is suggested throughout the period Jan-Mar with the biggest improvement
indicated in March -- except for coastal Southern California. A map showing the composite
precipitation anomaly in inches for the period <a href="wxdata1314/AfterWolter_PrecipCompOctDecInPDOAMO2014b.png" rel="wximage" target="_blank">October
to March</a> was also generated.
</p>
<p>
<span class="dropcap">W</span>hile today's medium range forecasts and 6-10 day and
8-14 day precipitation outlooks aren't particularly encouraging there are some straws
to grasp. The <a href="http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.shtml" target="_blank">AO
Index,</a> which has been positive for most of the rainy season is now negative and
the <a href="wxdata1314/gwo_90d010114b.gif" rel="wximage" target="_blank">Global Wind
Oscillation</a> (GWO) is in its first full orbit into positive AAM territory in several
months. Whether these changes eventually result in rain for Southern California we'll
just have to see.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<p>
</p>
</div>
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<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateGlobal Wind Oscillation (GWO)Los Angeles rainfallprecipitation outlookweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=880b72b1-8553-467a-8cb0-ccaa8254f34bhttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,880b72b1-8553-467a-8cb0-ccaa8254f34b.aspxGary Valle

CPC Dec-Jan-Feb Precipitation Outlook
Released October 17, 2013.

Updated November 5, 2013. My mistake -- a spreadsheet range error -- thanks
for the heads up Reg! The driest January 1 to November 1 for Downtown Los Angeles
was in 1972 with 0.92 inch. Here are the driest ten years for that period:

An energetic
upper level low brought the first widespread precipitation of the rain season
to Southern California October 9, with rain at the lower elevations and some snow
in the local mountains. Rainfall
amounts varied widely, ranging from a trace in some areas to over an inch in the
mountains.

Downtown Los Angeles (USC) recorded only 0.04 inch for
the storm, bringing the water year rainfall total to 0.13 inch, which is 0.31 inch
below normal. Downtown Los Angeles has recorded only 2.76 inches of rain since January
1. This is one of the driest January 1 - October 20 in Los Angeles over the past 135
years! To get out of the bottom ten for calendar year rainfall Los Angeles needs about
3.5 inches of rain by December 31. Normal rainfall for November is 1.04 inches and
for December is 2.33 inches.

For months I've been monitoring climate data and forecasts
looking for something on which to base a 2013-14 Winter precipitation Outlook. Historically
ENSO has played the major role in Southern California rain season weather, with El
Nino conditions generally producing wetter weather and La Nina conditions generally
drier. But ENSO conditions are currently Neutral and are expected to remain so through
the end of the year.

Most climate models forecast
slow warming of SSTs in the equatorial Pacific (NINO 3.4 region) over the next
several months, but at this time of the year it would be very unusual to have substantial
warming. The CPC/IRI
ENSO Forecasts from IRI's October Quick Look indicate the probability of an El
Nino developing before the end of the year is less than 20% -- and 20% seems high.

One computer model that at times has been forecasting
above average precipitation in Southern California this Winter is the Climate Forecast
System version 2 (CFSv2). The CFSv2 is fully coupled ocean-atmosphere-land-sea ice
model used to forecast parameters such as sea surface temperature, temperature and
precipitation rate. While skillful at predicting tropical SSTs, the CFSv2 generally
performs very poorly when forecasting precipitation over land, so forecasts such as
this earlier
one for Dec-Jan-Feb must be viewed somewhat skeptically.

Another glass half-full observation is that the Madden-Julian
Oscillation (MJO) has been relatively active this year and if this activity continues
it provides recurring opportunities for enhanced U.S. West Coast precipitation. The
downside is that it can result in periods of dry weather as well.

With the ocean and atmosphere neutral there's just not
much on which to base a rain season forecast. As a result of the government shutdown
the release of the official NOAA 2013-14 Winter Outlook has been delayed until November.
The October CPC outlook is usually the basis of the initial official NOAA U.S. Winter
Outlook. The U.S.
Dec-Jan-Feb Precipitation Outlook, released October 17, calls for an equal chance
of below average, average, or above average precipitation for all of California. We'll
see!

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
First Widespread Precipitation of the Rain Season. One of the Driest Calendar Years for Los Angeles in 135 Years! Southern California 2013-14 Winter Precipitation Outlook.http://www.sierraphotography.com/wxnotes/PermaLink,guid,880b72b1-8553-467a-8cb0-ccaa8254f34b.aspxhttp://www.sierraphotography.com/wxnotes/FirstWidespreadPrecipitationOfTheRainSeasonOneOfTheDriestCalendarYearsForLosAngelesIn135YearsSouthernCalifornia201314WinterPrecipitationOutlook.aspx
Sun, 20 Oct 2013 22:31:26 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="CPC Dec-Jan-Feb Precipitation Outlook, released October 17, 2013." href="wxdata1314/cpc_precipDJF101713b.gif" rel="wximage"> <img border="0" alt="CPC Dec-Jan-Feb Precipitation Outlook" src="wxdata1314/cpc_precipDJF101713c.gif" width="300" height="279" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">CPC Dec-Jan-Feb Precipitation Outlook<br />
Released October 17, 2013.</span>
</p>
</div>
<p>
<i>Updated November 5, 2013</i>. My mistake -- a spreadsheet range error -- thanks
for the heads up Reg! The driest January 1 to November 1 for Downtown Los Angeles
was in 1972 with 0.92 inch. Here are the driest ten years for that period:
</p>
<p>
1. 1972 0.92<br />
2. 2002 1.62<br />
3. 1984 1.93<br />
4. 1961 2.37<br />
5. 1971 2.39<br />
6. 1947 2.45<br />
7. 2013 2.78<br />
8. 1894 2.89<br />
9. 1953 2.89<br />
10. 2007 3.37<br />
</p>
<p>
<span class="dropcap">A</span>n <a href="wxdata1314/goes15wv100913_2100zb.gif" rel="wximage" target="_blank">energetic
upper level low</a> brought the first widespread precipitation of the rain season
to Southern California October 9, with rain at the lower elevations and some snow
in the local mountains. <a href="wxdata1314/RRMLOX101013_0305PDT.pdf" target="_blank">Rainfall
amounts varied widely</a>, ranging from a trace in some areas to over an inch in the
mountains.
</p>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) recorded only 0.04 inch for
the storm, bringing the water year rainfall total to 0.13 inch, which is 0.31 inch
below normal. Downtown Los Angeles has recorded only 2.76 inches of rain since January
1. This is one of the driest January 1 - October 20 in Los Angeles over the past 135
years! To get out of the bottom ten for calendar year rainfall Los Angeles needs about
3.5 inches of rain by December 31. Normal rainfall for November is 1.04 inches and
for December is 2.33 inches.
</p>
<p>
<span class="dropcap">F</span>or months I've been monitoring climate data and forecasts
looking for something on which to base a 2013-14 Winter precipitation Outlook. Historically
ENSO has played the major role in Southern California rain season weather, with El
Nino conditions generally producing wetter weather and La Nina conditions generally
drier. But ENSO conditions are currently Neutral and are expected to remain so through
the end of the year.
</p>
<p>
<span class="dropcap">M</span>ost climate models <a href="wxdata1314/IRI_CPC_PredPlume091813b.gif" rel="wximage" target="_blank">forecast
slow warming of SSTs</a> in the equatorial Pacific (NINO 3.4 region) over the next
several months, but at this time of the year it would be very unusual to have substantial
warming. The <a href="wxdata1314/CPC_IRI_Consensus101013b.gif" rel="wximage" target="_blank">CPC/IRI
ENSO Forecasts</a> from IRI's October Quick Look indicate the probability of an El
Nino developing before the end of the year is less than 20% -- and 20% seems high.
</p>
<p>
<span class="dropcap">O</span>ne computer model that at times has been forecasting
above average precipitation in Southern California this Winter is the Climate Forecast
System version 2 (CFSv2). The CFSv2 is fully coupled ocean-atmosphere-land-sea ice
model used to forecast parameters such as sea surface temperature, temperature and
precipitation rate. While skillful at predicting tropical SSTs, the CFSv2 generally
performs very poorly when forecasting precipitation over land, so forecasts such as
this <a href="wxdata1314/usPrecSeaMaskDJF_100313_101213b.gif" rel="wximage" target="_blank">earlier
one for Dec-Jan-Feb</a> must be viewed somewhat skeptically.
</p>
<p>
<span class="dropcap">A</span>nother glass half-full observation is that the Madden-Julian
Oscillation (MJO) has been relatively active this year and if this activity continues
it provides recurring opportunities for enhanced U.S. West Coast precipitation. The
downside is that it can result in periods of dry weather as well.
</p>
<p>
<span class="dropcap">W</span>ith the ocean and atmosphere neutral there's just not
much on which to base a rain season forecast. As a result of the government shutdown
the release of the official NOAA 2013-14 Winter Outlook has been delayed until November.
The October CPC outlook is usually the basis of the initial official NOAA U.S. Winter
Outlook. The <a href="wxdata1314/cpc_precipDJF101713b.gif" rel="wximage" target="_blank">U.S.
Dec-Jan-Feb Precipitation Outlook</a>, released October 17, calls for an equal chance
of below average, average, or above average precipitation for all of California. We'll
see!
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
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<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)La NinaLos Angeles rainfallMadden-Julian Oscillation (MJO)precipitation outlookrecord rainfallSierra snowpackweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=03d68b8e-678a-49be-b3f6-107408529808http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,03d68b8e-678a-49be-b3f6-107408529808.aspxGary Valle

MIRS IWV All Satellites
December 2, 2012 1800 UTC Preceding 12 hours.

If you were to only look at the Global
Wind Oscillation (GWO) for November you might think our 2012-2013 El Nino hadn't
flopped. The relative AAM anomaly peaked at about 1.4 around November 20, which is
the highest it's been since the El Nino of 2009-2010.

Most of the AAM was added in the NH between
15°N and 30°N. This led to the development of a high amplitude mid-Pacific ridge,
and undercutting of the ridge by the westerlies. This enabled a low near the dateline
to tap tropical moisture and relay
it into the circulation of a large eastern Pacific low. This linkage provided
the moisture necessary to create the atmospheric rivers that produced excessive precipitation
in Northern and Central California last week.

Over the 5-day period ending Monday morning (December
3) Northern and Central California recorded double-digit precipitation totals with
several stations recording rainfall amounts in excess of 15 inches. Here are archived
Public Information Statements issued by NWS
San Francisco Bay Area/Monterey and NWS
Eureka with some of the phenomenal precipitation totals recorded in those areas.
This AHPS
Precipitation Analysis shows the observed precipitation in the western U.S. for
the 7-day period ending Monday morning.

New forecast methods developed by NOAA's
ESRL PSD using satellite-derived and GFS medium range forecast data indicated
high levels of water vapor transport early
Friday and early
Sunday. This typically characterizes AR events. This Evaluation
of GFS Forecast Fields (PDF) shows the observed Integrated Water Vapor (IWV) for
December 2, the corresponding analysis, and the 1-day to 5-day forecasts.

System dynamics were much weaker in Southern California,
and the IWV content of the atmospheric rivers was less. (Friday
IPW and Sunday
IPW). Even so orographically favored areas were still able to wring several inches
of rain from the moist flow. From Tuesday night to Monday morning Opids Camp recorded
3.02 inches, White Ledge Peak 4.09 inches, Refugio Pass 4.61 inches, and Rocky Butte
8.51 inches.

Over the same period Downtown Los Angeles (USC) recorded
1.03 inches, bringing the water year total to 1.36 inches. As of today that's 1.08
inch less than normal. Here's an archived copy of a NWS
compilation of preliminary rainfall totals in our area.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
November AAM Highest Since El Nino of 2009-10. Atmospheric Rivers Produce Heavy Precipitation in Central and Northern California.http://www.sierraphotography.com/wxnotes/PermaLink,guid,03d68b8e-678a-49be-b3f6-107408529808.aspxhttp://www.sierraphotography.com/wxnotes/NovemberAAMHighestSinceElNinoOf200910AtmosphericRiversProduceHeavyPrecipitationInCentralAndNorthernCalifornia.aspx
Sun, 09 Dec 2012 01:30:17 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="MIRS Integrated Water Vapor, December 2, 2012 1800 UTC for the preceeding 12 hours." href="http://www.sierraphotography.com/wxnotes/wxdata1213/12337_18utc_12h-ave_iwv_mirs_ALL.png" rel="wximage"> <img border="0" alt="MIRS Integrated Water Vapor, December 2, 2012 1800 UTC for the preceeding 12 hours." src="http://www.sierraphotography.com/wxnotes/wxdata1213/12337_18utc_12h-ave_iwv_mirs_ALLc.png" width="300" height="225" /> </a> <img alt="Click" src="http://www.sierraphotography.com/wxnotes/images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">MIRS IWV All Satellites<br />
December 2, 2012 1800 UTC Preceding 12 hours.</span>
</p>
</div>
<p>
<span class="dropcap">I</span>f you were to only look at the <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/gwo_110112_120512b.png" rel="wximage" target="_blank">Global
Wind Oscillation (GWO) for November</a> you might think our 2012-2013 El Nino hadn't
flopped. The relative AAM anomaly peaked at about 1.4 around November 20, which is
the highest it's been since the El Nino of 2009-2010.
</p>
<p>
<span class="dropcap">M</span>ost of the AAM was added in the NH <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/ESRL_PSDglaam.sig.90day120512b.gif" rel="wximage" target="_blank">between
15°N and 30°N</a>. This led to the development of a high amplitude mid-Pacific ridge,
and undercutting of the ridge by the westerlies. This enabled a low near the dateline
to tap tropical moisture and <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/GFS_700pw_npac_113012_12zb.gif" rel="wximage" target="_blank">relay
it into the circulation of a large eastern Pacific low</a>. This linkage provided
the moisture necessary to create the atmospheric rivers that produced excessive precipitation
in Northern and Central California last week.
</p>
<p>
<span class="dropcap">O</span>ver the 5-day period ending Monday morning (December
3) Northern and Central California recorded double-digit precipitation totals with
several stations recording rainfall amounts in excess of 15 inches. Here are archived
Public Information Statements issued by <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/PNSMTR120312_1101PST.pdf" target="_blank">NWS
San Francisco Bay Area/Monterey</a> and <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/PNSEKA120312_1230PST.pdf" target="_blank">NWS
Eureka</a> with some of the phenomenal precipitation totals recorded in those areas.
This <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/AHPS7dayPrecipWest120312_12zb.jpg" rel="wximage" target="_blank">AHPS
Precipitation Analysis</a> shows the observed precipitation in the western U.S. for
the 7-day period ending Monday morning.
</p>
<p>
<span class="dropcap">N</span>ew forecast methods developed by <a href="http://www.esrl.noaa.gov/psd/psd2/coastal/satres/ar_detect.html" target="_blank">NOAA's
ESRL PSD</a> using satellite-derived and GFS medium range forecast data indicated
high levels of water vapor transport <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/20121129_12_gfs_024_xport.AR.png" rel="wximage" target="_blank">early
Friday</a> and <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/20121129_12_gfs_072_xport.AR.png" rel="wximage">early
Sunday</a>. This typically characterizes AR events. This <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/ESRL_PSD_ARDetectionEval120212.pdf" target="_blank">Evaluation
of GFS Forecast Fields</a> (PDF) shows the observed Integrated Water Vapor (IWV) for
December 2, the corresponding analysis, and the 1-day to 5-day forecasts.
</p>
<p>
<span class="dropcap">S</span>ystem dynamics were much weaker in Southern California,
and the IWV content of the atmospheric rivers was less. (<a href="http://www.sierraphotography.com/wxnotes/wxdata1213/SSMIS_IWV_12336.am.AR.120112b.png" rel="wximage" target="_blank">Friday
IPW</a> and <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/SSMIS_IWV_12338.am.AR.120312b.png" rel="wximage" target="_blank">Sunday
IPW</a>). Even so orographically favored areas were still able to wring several inches
of rain from the moist flow. From Tuesday night to Monday morning Opids Camp recorded
3.02 inches, White Ledge Peak 4.09 inches, Refugio Pass 4.61 inches, and Rocky Butte
8.51 inches.
</p>
<p>
<span class="dropcap">O</span>ver the same period Downtown Los Angeles (USC) recorded
1.03 inches, bringing the water year total to 1.36 inches. As of today that's 1.08
inch less than normal. Here's an archived copy of a <a href="http://www.sierraphotography.com/wxnotes/wxdata1213/RRMLOX120312_1715PST.pdf" target="_blank">NWS
compilation of preliminary rainfall totals</a> in our area.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
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<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.El NinoGlobal Wind Oscillation (GWO)Los Angeles rainfallweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=4f982d57-459d-4966-8061-e6e2eb7bb409http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,4f982d57-459d-4966-8061-e6e2eb7bb409.aspxGary Valle

In a post last June I mentioned that the atmosphere wasn't
responding to warming Pacific equatorial SSTs. At that time normalized relative AAM
values had dropped to around -2 sigma. Although El Nino-like SST conditions developed
in the equatorial Pacific in July and persisted in August, the atmospheric
component (AAM) did not follow suit. The average AAM for the period July-September
was less than any other El Nino year going back to 1950. (See chart below.)

Following a relative rapid 2 sigma increase over a period
of six months, the July/August value of the Multivariate
ENSO Index (MEI) dropped from 1.139 to 0.579, and its rank for the season dropped
from just below a 'strong' El Nino to just below a 'weak' El Nino. Over the last month SST
Anomaly in Nino Region 3.4 has dropped 0.6°C. A review of the ONI record reveals
that a drop in the index, which is based on a 3 month running mean of Nino 3.4 anomaly,
has not occurred before the Sep-Oct-Nov season during a warm episode.

As of mid September most models were
still forecasting development of weak El Nino conditions. The IRI/CPC
Plume-based ENSO Forecast puts the probability of El Nino conditions in the Sep-Oct-Nov
season at a little over 80%! The probability of Neutral conditions is pegged at a
little under 20%. The chance of returning to La Nina conditions is considered virtually
nil. Going back to 1950, year two La Nina conditions almost always transition either
back to La Nina conditions or to El Nino conditions. Depending on the climatology
used there is either one (1985-86) or no cases of a transition to Neutral conditions
from a second year La Nina.

Many dynamical
model MJO forecasts are predicting a developing MJO signal in the Western Pacific,
and that appears to be occurring. Velocity potential loops and Pacific Basin stitched
satellite imagery show enhanced convection west of the date line, and today's MJO
phase space plot from CAWCR/BOM shows a signal beginning to emerge. On the wind
side, Mountain
torques are over +4 sigma and Coriolis torque is at -2 sigma. Whether the (apparently)
emerging MJO will help reboot our fading El Nino remains to be seen.

Update Friday, October 5, 2012. Eastward-propagating MJO-like signal didn't
evolve as forecast
by GFS (and several other models). Here's today's MJO
phase space plot from CAWCR/BOM. Large swings in the magnitude of Mountain and
Coriolis torques have continued. Relative AAM remains at about -1 sigma. The Early
October CPC/IRI Consensus Probabilistic ENSO Forecast indicates an increasing
chance of Neutral conditions developing over the next several months, but still gives
an edge to El Nino conditions developing before the end of 2012.

Following is a chart comparing 2012-13 to warm ENSO episodes
that have occurred since 1950. The warm episodes are based on the revised Oceanic
Niño Index (ONI) based on multiple-centered 30 year base periods and are those specified
in the CPC's tabulation of Cold & Warm Episodes by Season. A description of the
parameters follows the chart. With the exception of years prior to 1957, a GWO phase
space plot is included for each warm episode.

Jul-Sep AAM & Nov-Mar AAM: The mean of the global relative atmospheric
angular momentum anomaly for the periods July 1 to September 30 amd November 1 to
March 31 of the following year. Data is from the GWO phase space data file linked
on the Global
Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann
and Berry, 2008.

Downtown Los Angeles (USC) will end the the 2011-2012
water year (July 1 to June 30) having recorded 8.69 inches of rain. This is about
58% of the 1981-2010 normal of 14.93 inches. The deficit of 6.24 inches is a little
more than the 5-6 inch deficit recorded in a selection
of similar second year La Nina years. According to data compiled by the NWS Santa
Barbara will end the water year at about 66% of normal; Camarillo/Oxnard at 57%; Burbank
Airport at 51%; LAX at 59%; and Long Beach Airport at 62%.

This TAO/Triton plot of Pacific equatorial SST and anomaly
clearly depicts the evolution of our two year La Nina and the recent transition to
warmer conditions. Is an El Nino in the works for this Winter? According to the Multivariate
ENSO Index (MEI) a transition to El Nino conditions may already be underway. The
April/May value of the MEI was +0.706. This is already within the range of a weak
El Niño ranking. In his June 6 discussion of the MEI climatologist Klaus Wolter noted
the last month's increase in the MEI was the 6th highest increase for this time of
year since 1950. He also pointed out that it was the 4th monthly increase of this
caliber in a row -- second only to the record of six consecutive large monthly increases
in 1997 at the beginning of the mega El Nino of 1997-98. It will be very interesting
to see if the string of large increases in the MEI continues with the May/June value.

While the ocean seems to be on board with the El Nino
idea, the atmosphere appears to be balking -- at least for the moment. As of June
24, the
AAM component of the GWO was down around -2.0, which is nearly as low as it's
been during year two of the 2010-2012 La Nina. A positive value of AAM is generally
associated with El Nino conditions.

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Downtown Los Angeles Ends 2011-2012 Water Year Six Inches Below Normal Rainfall. Is an El Nino in the Works for This Winter?http://www.sierraphotography.com/wxnotes/PermaLink,guid,a3e52768-20db-4c98-a8ea-206305ba9b2b.aspxhttp://www.sierraphotography.com/wxnotes/DowntownLosAngelesEnds20112012WaterYearSixInchesBelowNormalRainfallIsAnElNinoInTheWorksForThisWinter.aspx
Sat, 30 Jun 2012 23:27:44 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="TAO/TRITON Time-Longitude Plot Pacific Equatorial SST and Anomaly - Saturday, June 30, 2012" href="wxdata1112/time_lon_EQ_hf_sst_sst_mean_anom_201006_201206_2012063013.gif" rel="wximage" target="_blank"> <img border="0" alt="TAO/TRITON Time-Longitude Plot SST and Anomaly" src="wxdata1112/time_lon_EQ_hf_sst_sst_mean_anom_201006_201206_2012063013c.gif" width="350" height="252" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">TAO/TRITON Time-Longitude Plot of SST and Anomaly<br />
Saturday, June 30, 2012</span>
</p>
</div>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) will end the the 2011-2012
water year (July 1 to June 30) having recorded 8.69 inches of rain. This is about
58% of the 1981-2010 normal of 14.93 inches. The deficit of 6.24 inches is a little
more than the 5-6 inch deficit recorded in a <a href="http://www.sierraphotography.com/wxnotes/RecordSettingEarlySeasonStormLaNinaConsolidatesHowMightASecondYearLaNinaImpact2011USWinterPrecipitation.aspx" target="_blank">selection
of similar second year La Nina years</a>. According to data compiled by the NWS Santa
Barbara will end the water year at about 66% of normal; Camarillo/Oxnard at 57%; Burbank
Airport at 51%; LAX at 59%; and Long Beach Airport at 62%.
</p>
<p>
<span class="dropcap">T</span>his TAO/Triton plot of Pacific equatorial SST and anomaly
clearly depicts the evolution of our two year La Nina and the recent transition to
warmer conditions. Is an El Nino in the works for this Winter? According to the <a href="http://www.esrl.noaa.gov/psd/enso/mei/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) a transition to El Nino conditions may already be underway. The
April/May value of the MEI was +0.706. This is already within the range of a weak
El Niño ranking. In his June 6 discussion of the MEI climatologist Klaus Wolter noted
the last month's increase in the MEI was the 6th highest increase for this time of
year since 1950. He also pointed out that it was the 4th monthly increase of this
caliber in a row -- second only to the record of six consecutive large monthly increases
in 1997 at the beginning of the mega El Nino of 1997-98. It will be very interesting
to see if the string of large increases in the MEI continues with the May/June value.
</p>
<p>
<span class="dropcap">W</span>hile the ocean seems to be on board with the El Nino
idea, the atmosphere appears to be balking -- at least for the moment. As of June
24, <a href="wxdata1112/psd_gwo_90d_062412b.gif" rel="wximage" target="_blank">the
AAM component of the GWO</a> was down around -2.0, which is nearly as low as it's
been during year two of the 2010-2012 La Nina. A positive value of AAM is generally
associated with El Nino conditions.
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=a3e52768-20db-4c98-a8ea-206305ba9b2b" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)La NinaLos Angeles rainfallMultivariate ENSO Index (MEI)weatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=f27fd81c-285a-4914-9409-d1eb67983fc8http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,f27fd81c-285a-4914-9409-d1eb67983fc8.aspxGary Valle

ESRL/PSD Analog 8-14 Day Probabilistic Precipitation Forecast
Probability of more than 25mm precipitation from 03/04/12 to 03/10/12.

Wednesday Downtown Los Angeles' water year rainfall total
fell below 50% of normal for the date. With only 5.22 inches of rain in the bucket
it looks like we're headed toward the driest rain season since the record-setting
dry water year of 2006-2007, when a meager 3.21 inches was recorded. If Los Angeles
ends the rain year (June 30) with less than 7.16 inches of precipitation, the 2011-2012
water year would be one of the ten driest on record.

It's been dry throughout most of Southern California
and much of the state. According to data compiled by the NWS Burbank's water year
total now stands at a paltry 34% of normal; Long Beach 49% of normal; Camarillo 42%
of normal; Santa Barbara 56% of normal; and Paso Robles 49% of normal. Southernmost
California has fared a little better with San Diego at about 79% of normal for the
date. Central California rainfall is also well below average with San Francisco at
35% of the normal, San Jose at 26% and Sacramento at 40%.

I received an email recently from a reader asking if
I thought a March Miracle was likely this year. Keeping in mind the chaotic nature
of weather, and that low probability events do sometimes occur, the short answer is
that I don't think it's likely we'll see higher than normal rainfall this March.

In a post in early October I discussed what the impact
of a second year La Nina might be on 2011-12 Winter precipitation in the continental
U.S. For a selection of seven second year La Ninas the coastal Southern California
climate division recorded about 5 to 6 inches less precipitation than normal for the
period November through March. If we take a look at March rainfall in that same selection
of second year La Ninas, four of the seven recorded less than 0.5 inch rain in March,
and only one was well above average -- 4.83 inches in March 1975.

On the climate side of things the active phase of the
MJO has been stalled
in the Indian Ocean, but the 15-day
ensemble ECMWF and several models forecast increased amplitude and eastward propagation.
As a result of strong negative East Asian and Tropical torque events, relative atmospheric
angular momentum is dropping like a rock, with the GWO
taking a big dive into La Nina territory. Should the MJO continue to propagate
and AAM increase over the next 2 weeks, perhaps we'll see the scenario necessary to
generate an extended Pacific jet strong enough to impact the West Coast.

Monday its looking like we may get a little rain and
possibly some lower elevation snow. Goes soundings and model data indicate the Pacific
system is moisture-starved, but it is quite cold and is forecast to have strong dynamics.
A GOES sounding near the systems core showed a 500mb temp of -30°C. Precipitable water
values in the circulation around the low were around 0.6 inch. With such cold air
aloft, and strong system dynamics, strong convection is a possibility. We'll see!

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Downtown Los Angeles Rainfall Drops Below 50% of Normal. What are the Chances of a March Miracle?http://www.sierraphotography.com/wxnotes/PermaLink,guid,f27fd81c-285a-4914-9409-d1eb67983fc8.aspxhttp://www.sierraphotography.com/wxnotes/DowntownLosAngelesRainfallDropsBelow50OfNormalWhatAreTheChancesOfAMarchMiracle.aspx
Sun, 26 Feb 2012 23:37:30 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="ESRL/PSD Analog 8-14 Day Probabilistic Precipitation Forecast" href="wxdata1112/PSDAnalog8-14gt25mm022612_00zb.jpg" rel="wximage" target="_blank"> <img border="0" alt="ESRL/PSD Analog 8-14 Day Probabilistic Precipitation Forecast" src="wxdata1112/PSDAnalog8-14gt25mm022612_00zc.jpg" width="300" height="183" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">ESRL/PSD Analog 8-14 Day Probabilistic Precipitation Forecast<br />
Probability of more than 25mm precipitation from 03/04/12 to 03/10/12.</span>
</p>
</div>
<p>
<span class="dropcap">W</span>ednesday Downtown Los Angeles' water year rainfall total
fell below 50% of normal for the date. With only 5.22 inches of rain in the bucket
it looks like we're headed toward the driest rain season since the record-setting
dry water year of 2006-2007, when a meager 3.21 inches was recorded. If Los Angeles
ends the rain year (June 30) with less than 7.16 inches of precipitation, the 2011-2012
water year would be one of the ten driest on record.
</p>
<p>
<span class="dropcap">I</span>t's been dry throughout most of Southern California
and much of the state. According to data compiled by the NWS Burbank's water year
total now stands at a paltry 34% of normal; Long Beach 49% of normal; Camarillo 42%
of normal; Santa Barbara 56% of normal; and Paso Robles 49% of normal. Southernmost
California has fared a little better with San Diego at about 79% of normal for the
date. Central California rainfall is also well below average with San Francisco at
35% of the normal, San Jose at 26% and Sacramento at 40%.
</p>
<p>
<span class="dropcap">I</span> received an email recently from a reader asking if
I thought a March Miracle was likely this year. Keeping in mind the chaotic nature
of weather, and that low probability events do sometimes occur, the short answer is
that I don't think it's likely we'll see higher than normal rainfall this March.
</p>
<p>
<span class="dropcap">I</span>n a post in early October I discussed what the impact
of a second year La Nina might be on 2011-12 Winter precipitation in the continental
U.S. For a selection of seven second year La Ninas the coastal Southern California
climate division recorded about 5 to 6 inches less precipitation than normal for the
period November through March. If we take a look at March rainfall in that same selection
of second year La Ninas, four of the seven recorded less than 0.5 inch rain in March,
and only one was well above average -- 4.83 inches in March 1975.
</p>
<p>
<span class="dropcap">C</span>urrent outlooks are not favorable for higher than average
March precipitation. The Climate Prediction Centers <a href="wxdata1112/CPC_610prcp022612b.gif" rel="wximage" target="_blank">6-10
Day Precipitation Outlook</a>, <a href="wxdata1112/CPC_814prcp022612b.gif" rel="wximage" target="_blank">8-14
Day Precipitation Outlook</a>, and <a href="wxdata1112/CPC_monthprcp022612b.gif" rel="wximage" target="_blank">One
Month Precipitation Outlook</a> all indicate below normal precipitation in Southern
California. The ESRL/PSD Analog Probabilistic Precipitation Forecast is also dry in
the 6-10 and <a href="wxdata1112/PSDAnalog8-14gt25mm022612_00zb.jpg" rel="wximage" target="_blank">8-14
day outlook period</a>, and the <a href="wxdata1112/PSD_EnsembleSpread022612_00zb.png" rel="wximage" target="_blank">PSD
Ensemble Spread</a> does not look encouraging.
</p>
<p>
<span class="dropcap">O</span>n the climate side of things the active phase of the
MJO has been <a href="wxdata1112/BofM_MJO_40day_022412b.gif" rel="wximage" target="_blank">stalled
in the Indian Ocean</a>, but the <a href="wxdata1112/ECMF_phase_51m_full022312b.gif" rel="wximage">15-day
ensemble ECMWF</a> and several models forecast increased amplitude and eastward propagation.
As a result of strong negative East Asian and Tropical torque events, relative atmospheric
angular momentum is dropping like a rock, with the <a href="wxdata1112/PSD_gwo_40d022412b.gif" rel="wximage" target="_blank">GWO
taking a big dive into La Nina territory</a>. Should the MJO continue to propagate
and AAM increase over the next 2 weeks, perhaps we'll see the scenario necessary to
generate an extended Pacific jet strong enough to impact the West Coast.
</p>
<p>
<span class="dropcap">M</span>onday its looking like we may get a little rain and
possibly some lower elevation snow. Goes soundings and model data indicate the Pacific
system is moisture-starved, but it is quite cold and is forecast to have strong dynamics.
A GOES sounding near the systems core showed a 500mb temp of -30°C. Precipitable water
values in the circulation around the low were around 0.6 inch. With such cold air
aloft, and strong system dynamics, strong convection is a possibility. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=f27fd81c-285a-4914-9409-d1eb67983fc8" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateGlobal Wind Oscillation (GWO)La NinaLos Angeles rainfallMadden-Julian Oscillation (MJO)precipitation outlookweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=fb930bd1-1865-42ce-aa40-50ea41c059b9http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,fb930bd1-1865-42ce-aa40-50ea41c059b9.aspxGary Valle

Following is a chart comparing the 2011-12 La Nina to other cold ENSO episodes that
have occurred since 1949. With the exception of 1961-62 and 2008-09 the cold episodes
are based on the Oceanic Niño Index (ONI) and are those specified in the CPC's tabulation
of Cold & Warm Episodes by Season. A description of the parameters follows the
chart. A GWO phase space plot is included for those cold episodes for which AAM data
is available. Data for 2011-12 will be updated periodically.

Year

Nov-Mar
AAM

Peak MEI4

Peak MEI Season

Peak
ONI

Peak ONI Season

L.A. Rain

GWO
Phase Plot

1949-501,2

--

-1.423

APRMAY

-1.7

DJF

9.94

--

1950-511

--

-1.247

NOVDEC

-1.0

NDJ, DJF

8.21

--

1954-551

--

-1.578

MAYJUN (54)

-1.2

ASO

11.94

--

1955-561

--

-2.276

MAYJUN (55)

-2.0

OND

16.00

--

1956-571

--

-1.516

MAYJUN (56)

-0.9

SON, OND

9.54

--

1961-623

-0.513

-1.093

DECJAN

-0.6

ASO, SON

18.79

1962-63

-1.259

-0.843

JANFEB

-0.7

OND, NDJ

8.38

1964-65

-1.145

-1.496

JULAUG

-1.2

SON, OND

13.69

1967-68

-0.770

-1.060

APRMAY

-0.9

JFM

16.58

1970-71

-0.976

-1.898

MARAPR

-1.3

DJF, JFM

12.32

1971-72

-0.173

-1.463

AUGSEP

-1.0

OND

7.17

1973-74

-1.331

-1.942

DECJAN

-2.1

NDJ

14.92

1974-75

-0.842

-1.255

OCTNOV

-0.9

OND

14.35

1975-76

-0.713

-2.000

SEPOCT

-1.7

OND, NDJ

7.22

1984-85

-0.597

-0.743

APRMAY

-1.1

NDJ

12.82

1988-89

-1.139

-1.591

AUGSEP

-1.9

OND, NDJ

8.08

1995-96

-0.227

-0.644

DECJAN

-0.7

OND to JFM

12.46

1998-99

-0.541

-1.233

JANFEB

-1.4

NDJ, DJF

9.09

1999-00

-0.781

-1.242

JANFEB

-1.6

NDJ, DJF

11.57

2000-01

-0.795

-.755

OCTNOV

-0.7

NDJ

17.94

2007-08

-1.010

-1.631

FEBMAR

-1.4

DJF, JFM

13.53

2008-093

-0.596

-.783

SEPOCT

-0.8

DJF

9.08

2010-11

-0.596

-2.037

AUGSEP

-1.4

SON, OND, NDJ

20.20

2011-125

-0.370

-1.046

DECJAN

-1.0

OND, NDJ

8.19

1. AAM and AAM tendency anomaly data not available.
2. Based on ONI values beginning with DJF 1949-50.
3. ONI did not meet threshold of 5 consecutive overlapping seasons.
4. MEI values are normalized and may change as new data is added. Specified values
were current as of April 24, 2012.
5. Data as of April 24, 2012.

Nov-Mar AAM: The mean of the global relative atmospheric angular
momentum anomaly for the period November 1 to March 31 of the following year. Data
is from the GWO phase space data file linked on the Global
Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann
and Berry, 2008.

For the past two years Los Angeles has recorded above
normal rainfall over the first six months of the water year (Jul. 1 to Dec. 31). So
far this year is following suit.

After a record-setting storm in early October in which
Downtown Los Angeles (USC) recorded over an inch or rain, a series of upper level
troughs have continued to bump up the rainfall total. The systems have tended to be
amplifying upper level troughs that split, typically transforming the southern half
of the trough into a difficult-to-forecast cut-off upper level low. The resulting
cut-off lows have then tracked over, along, or off the Southern California coast producing
varying amounts of rain.

Sunday's system was the fourth to produce measurable
rain in Los Angeles this November. A strong
cold front produced very heavy rain, resulting in flooded streets and highways
and resulting in a host of other weather-related problems. In the middle of it all
runners in the PCTR Santa Monica Mountains 9K, 18K, 30K and 50K were running
distances up to 31.5 miles on the trails of Pt. Mugu State Park.

Downtown Los Angeles (USC) recorded 0.90 inches for the
storm, bringing the water year total to 2.75 inches. This is 1.11 inch above the new
1981-2010 normal for rainfall from July 1 through November 22. Here are some additional
(preliminary) precipitation
totals from around the area, compiled by the NWS Los Angeles/Oxnard. More than
an inch above normal sounds like a lot, but as of today only guarantees Los Angeles
precipitation will be above normal through December 12.

Back on July 1 NOAA released
the new 1981-2010 climate normals, replacing the 1971-2000 normals that have been
used this past decade. Normals serve as a 30 year baseline average of climate variables
such as monthly and annual maximum, minimum, and mean temperature; and monthly and
annual total precipitation. For example, Downtown Los Angeles' new normal annual precipitation
total is now 14.93 inches, down from the 15.14 inches we've been using.

After dropping to -0.503 for July/August, and then to
-0.772 for August/September, the September/October value of the Multivariate
ENSO Index (MEI) has dropped a bit more to -.968 sigma. This is well within La
Nina territory, but almost one sigma less than last year's September/October value.
Plots of the Global
Wind Oscillation (GWO) for July
1 to November 19, 2011 and the same
period last year illustrate the year-to-year difference in the atmosphere's response
to La Nina conditions. So far, this year's response is consistent with a more active
MJO and a shift toward a more neutral ENSO state.

While there's still a chance of rain in Southern California
Thanksgiving Day, the forecast is looking better than it did a few days ago when rain
was considered likely. The difficulty in the forecast is yet another upper level trough splitting
into a cut-off upper level low. The 12z NAM forecasts the low to remain
offshore on Thanksgiving Day, and move into Northern Baja by the late afternoon.
The 09z SREF puts the probability of more than 0.01 inch of rain in coastal Southern
California for the 12
hours ending 4:00 pm Thursday at 10% - 30% and the chance
of more than 0.10 inch of rain at around 10%. A shift in the track of the low
toward the coast would significantly increase the chance of rain. We'll see!

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Los Angeles Starts Water Year Ahead of the Game - Again. Strong Cold Front Hammers Southland. La Nina and the GWO. Thanksgiving Day Rain?http://www.sierraphotography.com/wxnotes/PermaLink,guid,83eb7ce0-c90f-4253-8080-48e00398c492.aspxhttp://www.sierraphotography.com/wxnotes/LosAngelesStartsWaterYearAheadOfTheGameAgainStrongColdFrontHammersSouthlandLaNinaAndTheGWOThanksgivingDayRain.aspx
Wed, 23 Nov 2011 16:47:53 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="GOES-11 Water Vapor Image for Sunday, November 20, 2011 at 11:30 am PST" href="wxdata1112/goes11wv112011_1930zb.gif" rel="wximage" target="_blank"> <img border="0" src="wxdata1112/goes11wv112011_1930zc.gif" width="350" height="263" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">GOES-11 Water Vapor Image<br />
Sunday, November 20, 2011 - 11:30 am PST</span>
</p>
</div>
<p>
<span class="dropcap">F</span>or the past two years Los Angeles has recorded above
normal rainfall over the first six months of the water year (Jul. 1 to Dec. 31). So
far this year is following suit.
</p>
<p>
<span class="dropcap">A</span>fter a record-setting storm in early October in which
Downtown Los Angeles (USC) recorded over an inch or rain, a series of upper level
troughs have continued to bump up the rainfall total. The systems have tended to be
amplifying upper level troughs that split, typically transforming the southern half
of the trough into a difficult-to-forecast cut-off upper level low. The resulting
cut-off lows have then tracked over, along, or off the Southern California coast producing
varying amounts of rain.
</p>
<p>
<span class="dropcap">S</span>unday's system was the fourth to produce measurable
rain in Los Angeles this November. A <a href="wxdata1112/wsicompradar_112011_1930zb.gif" rel="wximage" target="_blank">strong
cold front produced very heavy rain</a>, resulting in flooded streets and highways
and resulting in a host of other weather-related problems. In the middle of it all
runners in the PCTR Santa Monica Mountains 9K, 18K, 30K and 50K were <a href="http://vimeo.com/32463662" target="_blank">running
distances up to 31.5 miles</a> on the trails of Pt. Mugu State Park.
</p>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) recorded 0.90 inches for the
storm, bringing the water year total to 2.75 inches. This is 1.11 inch above the new
1981-2010 normal for rainfall from July 1 through November 22. Here are some additional
(preliminary) <a href="wxdata1112/RRMLOX112011_2200PST.pdf" target="_blank">precipitation
totals</a> from around the area, compiled by the NWS Los Angeles/Oxnard. More than
an inch above normal sounds like a lot, but as of today only guarantees Los Angeles
precipitation will be above normal through December 12.
</p>
<p>
<span class="dropcap">B</span>ack on July 1 NOAA <a href="http://www.noaanews.noaa.gov/stories2011/20110629_newnormals.html" target="_blank">released
the new 1981-2010 climate normals</a>, replacing the 1971-2000 normals that have been
used this past decade. Normals serve as a 30 year baseline average of climate variables
such as monthly and annual maximum, minimum, and mean temperature; and monthly and
annual total precipitation. For example, Downtown Los Angeles' new normal annual precipitation
total is now 14.93 inches, down from the 15.14 inches we've been using.
</p>
<p>
<span class="dropcap">A</span>fter dropping to -0.503 for July/August, and then to
-0.772 for August/September, the September/October value of the <a href="http://www.esrl.noaa.gov/psd/enso/mei/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) has dropped a bit more to -.968 sigma. This is well within La
Nina territory, but almost one sigma less than last year's September/October value.
Plots of the <a href="http://www.esrl.noaa.gov/psd/map/clim/test_maproom.html" target="_blank">Global
Wind Oscillation</a> (GWO) for <a href="wxdata1112/gwo_080111_111911b.png" rel="wximage" target="_blank">July
1 to November 19, 2011</a> and the <a href="wxdata1112/gwo_080110_111910b.png" rel="wximage" target="_blank">same
period last year</a> illustrate the year-to-year difference in the atmosphere's response
to La Nina conditions. So far, this year's response is consistent with a more active
MJO and a shift toward a more neutral ENSO state.
</p>
<p>
<span class="dropcap">W</span>hile there's still a chance of rain in Southern California
Thanksgiving Day, the forecast is looking better than it did a few days ago when rain
was considered likely. The difficulty in the forecast is yet another upper level trough <a href="wxdata1112/nam_009_500_vort_ht_112311_12zb.gif" rel="wximage" target="_blank">splitting
into a cut-off upper level low</a>. The 12z NAM forecasts the low to <a href="wxdata1112/nam_027_500_vort_ht_112311_12zb.gif" rel="wximage" target="_blank">remain
offshore on Thanksgiving Day</a>, and move into Northern Baja by the late afternoon.
The 09z SREF puts the probability of more than 0.01 inch of rain in coastal Southern
California for the <a href="wxdata1112/SREFpcp12h_pr01_39_112311_09zb.gif" rel="wximage" target="_blank">12
hours ending 4:00 pm Thursday</a> at 10% - 30% and the <a href="wxdata1112/SREFpcp12h_pr1_39_112311_09zb.gif" rel="wximage" target="_blank">chance
of more than 0.10 inch</a> of rain at around 10%. A shift in the track of the low
toward the coast would significantly increase the chance of rain. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=83eb7ce0-c90f-4253-8080-48e00398c492" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateGlobal Wind Oscillation (GWO)La NinaLos Angeles rainfallMadden-Julian Oscillation (MJO)Multivariate ENSO Index (MEI)precipitation outlookweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=bd4674f6-87ba-48db-9248-047e3c22d8aahttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,bd4674f6-87ba-48db-9248-047e3c22d8aa.aspxGary Valle

Enhanced convection in the Western Pacific associated
with active phase of the MJO, and an extension
of the North Pacific Jet caused by a positive
East Asian mountain torque event appeared to have contributed to the unseasonable
amount of rainfall. As observed by Ed Berry (Atmospheric
Insights, Dec. 30, 2007), "...the MJO itself does not generate enough extratropical
westerly wind flow to allow the East Asian jet to impact the USA west coast. A strong
positive East Asian mountain torque needs to be involved, on average."

To get an idea of what the impact of a second year La
Nina might be on 2011-12 Winter precipitation in the continental U.S., the ESRL/PSD
US Climate Division Dataset Mapping Page was used to construct a map
of US composite precipitation anomalies for November to March for year two La
Ninas since 1949. The years included were based primarily on MEI rankings, and include
1950-51, 1955-56, 1962-63, 1971-72, 1974-75, 1999-2000 and 2008-09. The base period
was 1971-2000.

For this selection of years the coastal Southern California
climate division recorded about 5 to 6 inches less precipitation than normal for the
period November through March. The percent of normal water year rainfall recorded
at Downtown Los Angeles (USC) ranged from a low of 47% (1971, 7.17"), to a high of
106% (1955, 16.00"). The average rainfall at Los Angeles for these years was 70.5%
of normal, or 10.7".

More information about Southern California weather and
climate can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Record-Setting Early Season Storm. La Nina Consolidates. How Might a Second Year La Nina Impact 2011 U.S. Winter Precipitation?http://www.sierraphotography.com/wxnotes/PermaLink,guid,bd4674f6-87ba-48db-9248-047e3c22d8aa.aspxhttp://www.sierraphotography.com/wxnotes/RecordSettingEarlySeasonStormLaNinaConsolidatesHowMightASecondYearLaNinaImpact2011USWinterPrecipitation.aspx
Sat, 08 Oct 2011 21:05:22 GMT
<div id="mainwx">
<div class="fltlft">
<p align="center">
<a title="GOES-11 Water Vapor Image for Wednesday, October 5, 2011 at 11:30 am PDT" href="wxdata1112/goes11wv100511_1830zb.gif" rel="wximage" target="_blank"> <img border="0" src="wxdata1112/goes11wv100511_1830zc.gif" width="350" height="263" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">GOES-11 Water Vapor Image<br />
Wednesday, October 5, 2011 - 11:30 am PDT</span>
</p>
</div>
<p>
<span class="dropcap">A</span>n unseasonably deep upper level low, unusually strong
170+ kt Pacific jet, and associated cold front combined to produce record-setting
rainfall in Southern California Wednesday, October 5. Rainfall totals exceeded 1.0
inch in many areas.
</p>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) recorded 1.15 inches, setting
a new record for the date, and kick-starting the area's rainy season to 0.78 inch
above normal. <a href="wxdata1112/RERLOX100511_1800PDT.pdf" target="_blank">Rainfall
records for the date</a> were also set for LAX, Long Beach, Camarillo, Santa Barbara
and several other locations. It was the first measurable rainfall at Los Angeles since
June 17. Here are some preliminary precipitation totals from the <a href="wxdata1112/RRMLOX100511_1716PDT.pdf" target="_blank">NWS
Los Angeles/Oxnard,</a><a href="wxdata1112/PNSHNX100511_2251PDT.pdf" target="_blank">NWS
San Joaquin Valley/Hanford </a>and <a href="wxdata1112/RRMSGX100611_0609PDT.pdf" target="_blank">NWS
San Diego</a>.
</p>
<p>
<span class="dropcap">E</span>nhanced convection in the Western Pacific associated
with active phase of the MJO, and an <a href="wxdata1112/11100218_jetstream_norhem.gif" rel="wximage" target="_blank">extension
of the North Pacific Jet</a> caused by a <a href="wxdata1112/gltaum.90day.100511.gif" rel="wximage" target="_blank">positive
East Asian mountain torque</a> event appeared to have contributed to the unseasonable
amount of rainfall. As observed by Ed Berry (<a href="http://weatherclimatelink.blogspot.com/2007/12/getting-what-was-expected.html" target="_blank">Atmospheric
Insights, Dec. 30, 2007</a>), "...the MJO itself does not generate enough extratropical
westerly wind flow to allow the East Asian jet to impact the USA west coast. A strong
positive East Asian mountain torque needs to be involved, on average."
</p>
<p>
<span class="dropcap">T</span>he <a href="wxdata1112/gwo_40d_100511b.gif" rel="wximage" target="_blank">increase
in relative AAM shown by the GWO</a> not withstanding, La Nina conditions appear to
be consolidating in the equatorial Pacific. This <a href="wxdata1112/BofMPacificEqAnomaly100511b.gif" rel="wximage" target="_blank">four
month sequence of Pacific Ocean Equatorial Temperature anomaly cross sections</a> shows
substantial subsurface cooling from July 11 to September 11. The <a href="http://www.esrl.noaa.gov/psd/enso/mei/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) has dropped from -0.5 for July/August to -0.8 for the August/September
season. This drops the MEI from a rank of 16th last month to 13th this month, just
above the quintile definition of a moderate La Niña ranking. Last year the MEI for
August/September ranked 1st in the record since 1950. This <a href="wxdata1112/time_lon_EQ_hf_sst_sst_mean_anom_200910_201110_2011100716.gif" rel="wximage" target="_blank">TAO
time-longitude plot of SST and SST anomaly</a> shows less cooling than last year on
this date.
</p>
<p>
<span class="dropcap">T</span>o get an idea of what the impact of a second year La
Nina might be on 2011-12 Winter precipitation in the continental U.S., the <a href="http://www.esrl.noaa.gov/psd/data/usclimdivs/" target="_blank">ESRL/PSD
US Climate Division Dataset Mapping Page</a> was used to construct a <a href="wxdata1112/LaNinaYear2CompPrecipAnom7cases092111b.png" rel="wximage" target="_blank">map
of US composite precipitation anomalies</a> for November to March for year two La
Ninas since 1949. The years included were based primarily on MEI rankings, and include
1950-51, 1955-56, 1962-63, 1971-72, 1974-75, 1999-2000 and 2008-09. The base period
was 1971-2000.
</p>
<p>
<span class="dropcap">F</span>or this selection of years the coastal Southern California
climate division recorded about 5 to 6 inches less precipitation than normal for the
period November through March. The percent of normal water year rainfall recorded
at Downtown Los Angeles (USC) ranged from a low of 47% (1971, 7.17"), to a high of
106% (1955, 16.00"). The average rainfall at Los Angeles for these years was 70.5%
of normal, or 10.7".
</p>
<p>
<span class="dropcap">M</span>ore information about Southern California weather and
climate can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<div class="clearfloat">
</div>
</div>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=bd4674f6-87ba-48db-9248-047e3c22d8aa" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateGlobal Wind Oscillation (GWO)La NinaLos Angeles rainfallMadden-Julian Oscillation (MJO)Multivariate ENSO Index (MEI)weatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=95952a3b-9a64-46c1-a666-d57ea9c50458http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,95952a3b-9a64-46c1-a666-d57ea9c50458.aspxGary Valle

Following is a chart comparing the 2010-11 La Nina to 22 other cold ENSO episodes
that have occurred since 1949. With the exception of 1961-62 and 2008-09, the cold
episodes are based on the Oceanic Niño Index (ONI) and are those specified in the
CPC's tabulation of Cold & Warm Episodes by Season. A description of the parameters
follows the chart. A GWO phase space plot is included for those cold episodes for
which AAM data is available.

Year

Nov-Mar
AAM

Peak MEI4

Peak MEI Season

Peak
ONI

Peak ONI Season

L.A. Rain

GWO
Phase Plot

1949-501,2

--

-1.423

APRMAY

-1.7

DJF

9.94

--

1950-511

--

-1.261

NOVDEC

-1.0

NDJ, DJF

8.21

--

1954-551

--

-1.578

MAYJUN (54)

-1.2

ASO

11.94

--

1955-561

--

-2.276

MAYJUN (55)

-2.0

OND

16.00

--

1956-571

--

-1.516

MAYJUN (56)

-0.9

SON, OND

9.54

--

1961-623

-0.511

-1.081

DECJAN

-0.6

ASO, SON

18.79

1962-63

-1.254

-0.849

JANFEB

-0.7

OND, NDJ

8.38

1964-65

-1.141

-1.496

JULAUG

-1.2

SON, OND

13.69

1967-68

-0.767

-1.060

APRMAY

-0.9

JFM

16.58

1970-71

-0.973

-1.898

MARAPR

-1.3

DJF, JFM

12.32

1971-72

-0.172

-1.463

AUGSEP

-1.0

OND

7.17

1973-74

-1.326

-1.937

DECJAN

-2.1

NDJ

14.92

1974-75

-0.839

-1.256

OCTNOV

-0.9

OND

14.35

1975-76

-0.711

-2.000

SEPOCT

-1.7

OND, NDJ

7.22

1984-85

-0.595

-0.743

APRMAY

-1.1

NDJ

12.82

1988-89

-1.135

-1.591

AUGSEP

-1.9

OND, NDJ

8.08

1995-96

-0.226

-0.641

DECJAN

-0.7

OND to JFM

12.46

1998-99

-0.539

-1.219

JANFEB

-1.4

NDJ, DJF

9.09

1999-00

-0.778

-1.228

JANFEB

-1.6

NDJ, DJF

11.57

2000-01

-0.795

-.747

OCTNOV

-0.7

NDJ

17.94

2007-08

-1.007

-1.619

FEBMAR

-1.4

DJF, JFM

13.53

2008-093

-0.594

-.783

SEPOCT

-0.8

DJF

9.08

2010-11

-0.595

-2.037

AUGSEP

-1.4

SON, OND, NDJ

20.20

1. AAM and AAM tendency anomaly data not available.
2. Based on ONI values beginning with DJF 1949-50.
3. ONI did not meet threshold of 5 consecutive overlapping seasons.
4. MEI values are normalized and may change as new data is added. Specified values
were current as of November 8, 2011.

Nov-Mar AAM: The mean of the global relative atmospheric angular
momentum anomaly for the period November 1 to March 31 of the following year. Data
is from the GWO phase space data file linked on the Global
Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann
and Berry, 2008.

Following a 26 day stretch in which the temperature at
Downtown Los Angeles was below normal 25 of the days, and several lowest maximum temperature
records were set around the area, temperatures have soared, and record high temperatures
for the date have been recorded at several locations.

On June 30, Downtown Los Angeles ended the water year
about 8% above normal. Some stations in the Los Angeles area recorded more than this
and some less. There was a wide range of values. For example, Long Beach Airport was
about 20% above normal and Santa Barbara Airport about 23% above; but Camarillo Airport
reported 31% below normal rainfall. Here's an AHPS graphic showing the percent
of normal precipitation in California and the Southwest for the year ending July
1 at 12z.

Equatorial Pacific SSTs have generally continued to cool.
According to the CPC's
Weekly ENSO Update, issued July 12, the latest weekly SST departures were -1.3°C
(Niño1+2), -1.0°C (Niño 3), -0.8°C (Niño 3.4), and -0.4°C (Niño 4). According to the
CPC, La Niña conditions occur "when the monthly Niño3.4 OISST departures meet or exceed
-0.5°C along with consistent atmospheric features. These anomalies must also be forecasted
to persist for 3 consecutive months."

Reflecting the transition from El Nino to La Nina conditions,
the Multivariate
ENSO Index (MEI) for May-June experienced an unprecedented drop for the time of
year, decreasing nearly 1 standard deviation to a value of -0.41. In addition, the Global
Wind Oscillation (GWO) has orbited about -2 SD down on the La Nina side of the
phase space plot, and with the atmosphere in a generally low momentum state, may be
in that neighborhood for a while.

The most recent IRI
ENSO Update, released July 15, projects "an approximately 80% probability for
continuing La Niña conditions, and a 20% probability for returning neutral ENSO conditions.
"

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Equatorial Pacific SSTs have continued to cool and TAO/TRITON
data shows -1.0°C or greater anomalies extending from 95°W to beyond 150°W. According
to the CPC's Weekly ENSO Update, issued June 21, the latest weekly SST departures
were -0.7°C (Niño1+2), -0.6°C (Niño 3), -0.5°C (Niño 3.4), and 0.0°C (Niño 4). An
anomaly of -0.5°C in the Niño 3.4 region is the threshold for La Nina conditions.

The Global Wind Oscillation (GWO) has spiraled well into
La Niña territory. The global relative atmospheric angular momentum anomaly is at
its lowest value since March 2008, during the La Niña of 2007-2008.

Based on equatorial Pacific SSTs, section plots, tradewinds
and cloudiness; and the GWO and AAM; a transition to La Nina conditions appears to
be underway.

It looks like Downtown Los Angeles (USC) will likely
end the July 1 - June 30 water year having recorded 16.36 inches of rain. This is
more than an inch above the 1971-2000 annual climate norm of 15.14 inches.

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

As forecast, an energetic upper low skirted
the Los Angeles area yesterday on its way south into
northern Baja, Mexico. As the low moved south, a vorticity lobe spinning around
the low arced into the Southern California coast, producing rain, thunderstorms, waterspouts,
and blustery winds.

Rain amounts were variable, generally ranging from about
0.25 inch to 0.75 inch around the Los Angeles area. Indicative of the convective nature
of the precipitation, Downtown Los Angeles (USC) recorded 0.42 inch, while a few miles
away LAX recorded only 0.18 inch for the storm. The water year total for Downtown
Los Angeles now stands at 14.66 inches -- only 0.48 inch less than the annual norm
of 15.14 inches. Here is an archived copy of NWS
Public Information Statement with some more rainfall amounts for this rain event.

Reflecting the enhancement of El Niño by the MJO at the
end of January, the Multivariate
ENSO Index (MEI) for January-February has increased to 1.5. As discussed by Klaus
Wolter, MEI originator, this is the highest value of the Jan-Feb MEI since the strong
El Niño of 1997-1998, and the fifth highest MEI value for Jan-Feb since 1950. This
places the El Nino of 2009-10 in the top 10% of MEI rankings for the season since
1950, and above the "strong" El Niño threshold, as measured by the MEI. Here is a chart
comparing the current El Niño to others since 1950.

The increase in the MEI corresponds to the increase in
relative AAM since mid January and underscores the potential role of the Global Wind
Oscillation (GWO) in assessing the response of the atmosphere to El Niño. It also
reinforces the notion that the El Niño phenomena is more than just warm SSTs in the
central equatorial Pacific. As we've seen several times in recent years, warm SST
anomalies in the Niño 3.4 region alone are not sufficient for evaluating an El Niño
and its potential impacts.

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Upper Low Skirts Los Angeles, Tracks Into Baja. Jan-Feb MEI Ranks Current El Nino in Top 10% Since 1950.http://www.sierraphotography.com/wxnotes/PermaLink,guid,91a2c430-1c52-490d-a60a-d5313389a00b.aspxhttp://www.sierraphotography.com/wxnotes/UpperLowSkirtsLosAngelesTracksIntoBajaJanFebMEIRanksCurrentElNinoInTop10Since1950.aspx
Mon, 08 Mar 2010 17:05:26 GMT
<p>
</p>
<table border="0">
<tbody>
<tr valign="top">
<td valign="top" nowrap="">
<center>
<p>
<a href="#"> <img onclick="MM_openBrWindow('wxdata0910/goes11ir030610_2300zb.gif','','resizable=yes,width=660,height=500');return false" border="0" src="wxdata0910/goes11ir030610_2300zc.gif" width="250" height="188" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">GOES-11 IR Satellite Image<br />
March 6, 2010 - 3:00 p.m. PST</span>
</p>
</center>
</td>
<td valign="top">
<p>
<span class="dropcap">A</span>s forecast, an energetic upper low <a href="wxdata0910/goes11ir030610_2300zb.gif" rel="wximage" title="Upper low skirting the Southern California coast.">skirted
the Los Angeles area</a> yesterday on its way south <a href="wxdata0910/goes11ir030710_2300zb.gif" target="_blank">into
northern Baja, Mexico</a>. As the low moved south, a vorticity lobe spinning around
the low arced into the Southern California coast, producing rain, thunderstorms, waterspouts,
and blustery winds.
</p>
<p>
<span class="dropcap">R</span>ain amounts were variable, generally ranging from about
0.25 inch to 0.75 inch around the Los Angeles area. Indicative of the convective nature
of the precipitation, Downtown Los Angeles (USC) recorded 0.42 inch, while a few miles
away LAX recorded only 0.18 inch for the storm. The water year total for Downtown
Los Angeles now stands at 14.66 inches -- only 0.48 inch less than the annual norm
of 15.14 inches. Here is an archived copy of <a href="wxdata0910/PNSLOX030710_1740PST.pdf" target="_blank">NWS
Public Information Statement</a> with some more rainfall amounts for this rain event.
</p>
</td>
</tr>
<tr valign="top">
<td valign="top" colspan="2">
<p>
<span class="dropcap">R</span>eflecting the enhancement of El Niño by the MJO at the
end of January, the <a href="http://www.esrl.noaa.gov/psd/people/klaus.wolter/MEI/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) for January-February has increased to 1.5. As discussed by Klaus
Wolter, MEI originator, this is the highest value of the Jan-Feb MEI since the strong
El Niño of 1997-1998, and the fifth highest MEI value for Jan-Feb since 1950. This
places the El Nino of 2009-10 in the top 10% of MEI rankings for the season since
1950, and above the "strong" El Niño threshold, as measured by the MEI. Here is a <a href="http://www.sierraphotography.com/wxnotes/HowDoesTheElNinoOf200910CompareToOtherWarmENSOEpisodesSince1950.aspx" target="_blank">chart
comparing the current El Niño to others since 1950</a>.
</p>
<p>
<span class="dropcap">T</span>he increase in the MEI corresponds to the increase in
relative AAM since mid January and underscores the potential role of the Global Wind
Oscillation (GWO) in assessing the response of the atmosphere to El Niño. It also
reinforces the notion that the El Niño phenomena is more than just warm SSTs in the
central equatorial Pacific. As we've seen several times in recent years, warm SST
anomalies in the Niño 3.4 region alone are not sufficient for evaluating an El Niño
and its potential impacts.
</p>
<p>
<span class="dropcap">M</span>ore information concerning Southern California weather
can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<p>
</p>
</td>
</tr>
</tbody>
</table>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=91a2c430-1c52-490d-a60a-d5313389a00b" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)Los Angeles rainfallMadden-Julian Oscillation (MJO)Multivariate ENSO Index (MEI)weatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=aff9877a-0802-40cc-902f-7eaccc11976ahttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,aff9877a-0802-40cc-902f-7eaccc11976a.aspxGary Valle

GOES-11 Water Vapor Image (UW-MAD)
February 25, 2010 - 7:00 a.m. PST

A weakening frontal band produced some light rain in
Southern California yesterday afternoon and evening. Precipitation amounts in the
Los Angeles area ranged from a trace to a few hundredths of an inch. Amounts were
higher to the north, closer to the surface low. A few stations in Santa Barbara and
San Luis Obispo counties recorded more than 0.5 inch and some recorded more than an
inch. Here is an archived copy of a NWS
Public Information Statement with some precipitation totals from around the area.

Today, a much
stronger Pacific storm system begins to impact the West Coast, with the highest
precipitation totals forecast for Northern California and the Sierra Nevada. BUFKIT
analysis of this morning's 12z NAM data for Van Nuys generates about 1.3 inch of rain,
beginning late Friday night and continuing into Saturday afternoon. The 18z NAM run
starts the rain a little earlier Friday night, and extends the period of precipitation
into Saturday evening. It produces about 1.8 inch of rain at Van Nuys over the period.
Today's 09z SREF indicated
a probability of about 50%-70% that precipitation in the Los Angeles area would
exceed 0.5 inch for the 24 hr. period ending Saturday afternoon at 4:00 p.m. Precipitable
water values approaching an inch and strong southerly low level inflow could produce
higher rain rates and precipitation totals on south to southwest facing foothill and
mountain slopes.

Yesterday's cold upper level low behaved about as expected, following
a track just off the coast. Because of the convective nature of the system, rainfall
amounts varied from under 0.25 inch to over 1.0 inch in some foothill and mountain
locations. About a foot of snow was reported at the mountain resorts. Here is a NWS
Public Information Statement with precipitation totals from around the area. Downtown
Los Angeles (USC) recorded 0.44 inches for the storm, increasing the water year total
to 13.2 inches. The is 4.78 inches above normal for the date.

Compared to the AHPS 90 Day Precipitation map
from about 40 days ago, a fairly typical El Niño precipitation pattern has emerged
in the West. Medium range models are projecting about a 7-10 day break in what has
turned out to be a busy rainy season in Southern California. Assuming these forecasts
verify, such a break could not come a better time for those threatened by mudslides
and debris flows. The recent enhancement of El Niño convection by the MJO, and the
ongoing phase 6-7-8 transition
of the GWO might have resulted in a wetter pattern, and this has occurred in similar
circumstances in past El Ninos.

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Southern California Catches a Break.http://www.sierraphotography.com/wxnotes/PermaLink,guid,a65428a8-d5a2-4c98-9e0b-1e949b63140c.aspxhttp://www.sierraphotography.com/wxnotes/SouthernCaliforniaCatchesABreak.aspx
Wed, 10 Feb 2010 23:34:58 GMT
<p>
</p>
<table border="0">
<tbody>
<tr valign="top">
<td valign="top" nowrap="">
<center>
<p>
<a href="#"> <img onclick="MM_openBrWindow('wxdata0910/AHPSPrecip90Day021010_12zb.jpg','','resizable=yes,width=641,height=386');return false" border="0" alt="AHPS 90 Day Precipitation (Percent of Normal) as of February 10, 2010 4:00 a.m. PST" src="wxdata0910/AHPSPrecip90Day021010_12zc.jpg" width="300" height="177" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">AHPS 90 Day Precipitation (Percent of Normal)<br />
February 10, 2010</span> 4:00 a.m. PST
</p>
</center>
</td>
<td valign="top">
<p>
<span class="dropcap">Y</span>esterday's cold upper level low behaved about as expected, <a href="wxdata0910/goes11wv020910_2330zb.gif" target="_blank">following
a track just off the coast</a>. Because of the convective nature of the system, rainfall
amounts varied from under 0.25 inch to over 1.0 inch in some foothill and mountain
locations. About a foot of snow was reported at the mountain resorts. Here is a <a href="wxdata0910/PNSLOX021010_1052PST.pdf" target="_blank">NWS
Public Information Statement</a> with precipitation totals from around the area. Downtown
Los Angeles (USC) recorded 0.44 inches for the storm, increasing the water year total
to 13.2 inches. The is 4.78 inches above normal for the date.
</p>
<p>
<span class="dropcap">C</span>ompared to the AHPS 90 Day Precipitation <a href="http://www.sierraphotography.com/wxnotes/2010/01/02/SouthernCaliforniaSqueezesAFewRaindropsOutOfAStubbornElNino.aspx" target="_blank">map
from about 40 days ago</a>, a fairly typical El Niño precipitation pattern has emerged
in the West. Medium range models are projecting about a 7-10 day break in what has
turned out to be a busy rainy season in Southern California. Assuming these forecasts
verify, such a break could not come a better time for those threatened by mudslides
and debris flows. The recent enhancement of El Niño convection by the MJO, and the
ongoing <a href="wxdata0910/gwo_110109_020810b.jpg" target="_blank">phase 6-7-8 transition
of the GWO</a> might have resulted in a wetter pattern, and this has occurred in similar
circumstances in past El Ninos.
</p>
</td>
</tr>
<tr valign="top">
<td valign="top" colspan="2">
<p>
<span class="dropcap">M</span>ore information concerning Southern California weather
can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<p>
</p>
</td>
</tr>
</tbody>
</table>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=a65428a8-d5a2-4c98-9e0b-1e949b63140c" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)Los Angeles rainfallMadden-Julian Oscillation (MJO)precipitation outlookweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=e9df2f9a-0a5e-4c58-ba4f-4e015f3c00e9http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,e9df2f9a-0a5e-4c58-ba4f-4e015f3c00e9.aspxGary Valle

UCAR NEXRAD Regional Composite Image
February 6, 2010 - 4:45 a.m. PST

Wet antecedent conditions and heavy rain early this morning
combined to amplify the amount of runoff from our latest Winter storm. In addition
to localized street flooding, mud and debris flows have occurred in the vicinity of
the Station Fire burn area. The trough associated with the system, and a second frontal
band are moving onshore this afternoon, and are producing some additional rainfall
in the Los Angeles area. Please refer to www.weather.gov/losangeles for
the latest warnings and weather information.

Yesterday's runs of the NAM/WRF did a pretty good job
of forecasting the
area of enhanced precipitation that developed overnight in Southern California. BUFKIT
analysis of 12z NAM data from yesterday generated about 2.4 inches of precipitation
at KLAX for the 24 hr. period ending early this morning. According to preliminary
NWS data, as of 10:00 a.m. LAX had recorded 2.31 inches for the storm, and Downtown
Los Angeles (USC) had recorded 2.84 inches. The water year total rainfall for Los
Angeles is now about 5 inches above normal. Here is a NWS
Public Information Statement with rainfall totals from around the area. (Link
will be updated as revised totals become available.)

The recent enhancement
of El Nino convection in the equatorial Pacific by the Madden-Julian Oscillation
(MJO) has triggered a strong atmospheric response. A Global
Wind Oscillation (GWO) phase space plot shows large increases in relative atmospheric
angular momentum (AAM) and AAM tendency. As a result of this increase, the average
relative AAM anomaly for the rain season to date is now positive. As mentioned in
this post
from December 2009, relative AAM is correlated with rain season precipitation
in Southern California. This suggests an increased likelihood of wet weather in Southern
California in the medium range outlook period.

So what happens next? The ECMWF and GFS projections have
not been particularly consistent. At the moment, it looks like a shortwave trough
could affect Southern California in the Tuesday evening or Wednesday timeframe and
then again Friday. We'll see how the week develops.

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Heavy Rain Triggers Mudslides and Debris Flows. Atmosphere Responding to Enhanced El Nino Convection.http://www.sierraphotography.com/wxnotes/PermaLink,guid,e9df2f9a-0a5e-4c58-ba4f-4e015f3c00e9.aspxhttp://www.sierraphotography.com/wxnotes/HeavyRainTriggersMudslidesAndDebrisFlowsAtmosphereRespondingToEnhancedElNinoConvection.aspx
Sat, 06 Feb 2010 23:09:12 GMT
<p>
</p>
<table border="0">
<tbody>
<tr valign="top">
<td valign="top" nowrap="">
<center>
<p>
<a href="#"> <img onclick="MM_openBrWindow('wxdata0910/UCAR_NEXRADcomp_020610_1245zb.jpg','','resizable=yes,width=1020,height=770');return false" border="0" alt="UCAR NEXRAD Regional Composite Image February 6, 2010 - 4:45 a.m. PST" src="wxdata0910/UCAR_NEXRADcomp_020610_1245zc.jpg" width="300" height="225" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">UCAR NEXRAD Regional Composite Image<br />
February 6, 2010 - 4:45 a.m. PST</span>
</p>
</center>
</td>
<td valign="top">
<p>
<span class="dropcap">W</span>et antecedent conditions and heavy rain early this morning
combined to amplify the amount of runoff from our latest Winter storm. In addition
to localized street flooding, mud and debris flows have occurred in the vicinity of
the Station Fire burn area. The trough associated with the system, and a second frontal
band are moving onshore this afternoon, and are producing some additional rainfall
in the Los Angeles area. Please refer to <a href="http://www.weather.gov/losangeles" target="_blank">www.weather.gov/losangeles</a> for
the latest warnings and weather information.
</p>
<p>
<span class="dropcap">Y</span>esterday's runs of the NAM/WRF did a pretty good job
of <a href="wxdata0910/nam_p24_024m_020510_18zb.gif" target="_blank">forecasting the
area of enhanced precipitation</a> that developed overnight in Southern California. <a href="wxdata0910/BUFKIT_KLAX_NAM_020510_12zb.gif" target="_blank">BUFKIT
analysis of 12z NAM data</a> from yesterday generated about 2.4 inches of precipitation
at KLAX for the 24 hr. period ending early this morning. According to preliminary
NWS data, as of 10:00 a.m. LAX had recorded 2.31 inches for the storm, and Downtown
Los Angeles (USC) had recorded 2.84 inches. The water year total rainfall for Los
Angeles is now about 5 inches above normal. Here is a <a href="wxdata0910/PNSLOX020610_2232PST.pdf" target="_blank">NWS
Public Information Statement</a> with rainfall totals from around the area. (Link
will be updated as revised totals become available.)
</p>
</td>
</tr>
<tr valign="top">
<td valign="top" colspan="2">
<p>
<span class="dropcap">T</span>he recent <a href="wxdata0910/200hPaVelPotentialAnom020510b.gif" target="_blank">enhancement
of El Nino convection</a> in the equatorial Pacific by the Madden-Julian Oscillation
(MJO) has triggered a strong atmospheric response. A <a href="wxdata0910/gwo_110109_020410b.jpg" target="_blank">Global
Wind Oscillation (GWO) phase space plot</a> shows large increases in relative atmospheric
angular momentum (AAM) and AAM tendency. As a result of this increase, the average
relative AAM anomaly for the rain season to date is now positive. As mentioned in
this <a href="http://www.sierraphotography.com/wxnotes/2009/12/16/SouthernCaliforniaElNinoImpactsAndTheGlobalWindOscillation.aspx" target="_blank">post
from December 2009</a>, relative AAM is correlated with rain season precipitation
in Southern California. This suggests an increased likelihood of wet weather in Southern
California in the medium range outlook period.
</p>
<p>
<span class="dropcap">S</span>o what happens next? The ECMWF and GFS projections have
not been particularly consistent. At the moment, it looks like a shortwave trough
could affect Southern California in the Tuesday evening or Wednesday timeframe and
then again Friday. We'll see how the week develops.
</p>
<p>
<span class="dropcap">M</span>ore information concerning Southern California weather
can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
</p>
<p>
</p>
</td>
</tr>
</tbody>
</table>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=e9df2f9a-0a5e-4c58-ba4f-4e015f3c00e9" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)Los Angeles rainfallMadden-Julian Oscillation (MJO)precipitation outlookweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=5b1b3549-faa7-4717-a145-4cf7c09565a5http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,5b1b3549-faa7-4717-a145-4cf7c09565a5.aspxGary Valle

Another strong
Westerly Wind Burst (WWB) is also occurring, and appears to be one of the mechanisms
associated with MJO enhancement of deep El Nino convection. This enhancement and resulting
feedback could slow the decline of, or even increase, equatorial Pacific SST anomalies
in the weeks ahead.

Both the ECMWF and the GFS are projecting a return to
a wet pattern in California next week. The first skirmish occurs in central and northern
California over the weekend, and then a transition to a much wetter, and possibly
persistent, pattern is forecast to occur during the week. We'll see!

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Following is a chart comparing the 2009-10 El Niño to other warm ENSO episodes that
have occurred since 1950. The warm episodes are based on the Oceanic Niño Index (ONI)
and are those specified in the CPC's tabulation of Cold & Warm Episodes by Season.
A description of the parameters follows the chart. With the exception of 1951-52,
a GWO phase space plot is included for each warm episode. Data for 2009-10 will be
updated periodically.

Year

Nov-Mar
AAM

Peak MEI

Peak MEI Season

Peak
ONI

Peak ONI Season

L.A. Rain

GWO
Phase Plot

1951-521

--

0.856

JULAUG

0.8

SON

26.21

--

1957-582

0.773

1.470

DECJAN, JANFEB

1.7

DJF

21.13

1963-64

0.046

0.858

OCTNOV, DECJAN

1.0

OND, NDJ

7.93

1965-66

-0.748

1.485

JULAUG

1.6

OND, NDJ

20.44

1968-69

0.513

0.834

JANFEB

1.0

DJF, JFM

27.47

1972-733

-0.239

1.804

JUNJUL

2.1

NDJ

21.26

1976-77

-0.828

1.046

AUGSEP

0.8

OND

12.31

1977-78

1.008

1.007

SEPOCT, OCTNOV

0.7

OND, NDJ, DJF

33.44

1982-83

2.337

3.109

FEBMAR

2.3

NDJ, DJF

31.25

1986-874

0.019

2.128

APRMAY

1.3

JFM

7.66

1987-884

1.000

2.013

JULAUG

1.6

JAS, ASO

12.48

1991-92

0.808

2.246

MARAPR

1.8

DJF

21.00

1994-95

0.764

1.346

SEPOCT

1.3

NDJ

24.35

1997-98

1.481

2.882

JULAUG

2.5

OND, NDJ

31.01

2002-03

0.324

1.230

DECJAN

1.5

OND

16.49

2004-05

0.747

0.924

FEBMAR

0.9

ASO

37.96

2006-07

-0.322

1.288

OCTNOV

1.1

OND, NDJ

3.21

2009-105

0.304

1.502

JANFEB

1.8

NDJ

16.36

1. AAM and AAM tendency anomaly data for 1951-52 not available.
2. AAM anomaly is average for Jan-Mar 1958.
3. Several MEI values were near 1.8 during 1972-73.
4. Continuous episode from JAS 1986 to JFM 1988.
5. Data as of June 30, 2010.

Nov-Mar AAM: The mean of the global relative atmospheric angular
momentum anomaly for the period November 1 to March 31 of the following year. Data
is from the GWO phase space data file linked on the Global
Synoptic Dynamic Model page of the PSD Map Room Climate Products. Reference Weickmann
and Berry, 2008.

Following several weeks of dry weather, a shift to a
wetter pattern brought much needed rain and snow to California this past week. The
pattern change was apparently induced by MJO enhancement of El Niño convection in
the equatorial Pacific.

Downtown Los Angeles recorded 1.78 inches of rain from
Thursday to Sunday, bringing the water year total to 4.81 inches. This is about 2.20
inches above normal for the date. Rainfall totals generally ranged from 2 to 4 inches
in the basin and valleys, and 2 to 6 inches in the mountains. Here's an archived
copy of a NWS Public Information Statement with rainfall totals from around the
area.

Will the current El Niño produce the expected seasonal
impacts in Southern California? A new tool that can help gain some insight into the
linkage of climate and weather is the Global
Wind Oscillation (GWO) phase space plot. Ed Berry repeatedly demonstrated the
usefulness of this tool in his blog Atmospheric
Insights. Although the blog has been discontinued, its content remains a valuable
resource.

The GWO is a recurring subseasonal phenomenon that involves
the transport and interchange of momentum in the earth-atmosphere system. It encompasses
the MJO and occurs on a similar timescale. Analogous to the MJO phase space plot,
but based on a framework of atmospheric angular momentum (AAM), the GWO phase space
plot is a measure global relative atmospheric angular momentum and it's tendency.
For details, see Weickmann
& Berry, 2008.

In a decade characterized by quirky El Niños, the El
Niño of 2009-10 has been acting like another odd one. From a Southern California perspective,
the concern has been that it might be like the El Niño of 2006-07 when Downtown Los
Angeles recorded only 3.21" of rain over the water year. In the early stages of the
El Niño of 2006 strong convection developed in the Indian Ocean during November, but
an MJO did not develop until a second
round of Indian Ocean convection occurred in mid December. Relative AAM remained
negative, and in terms of the atmosphere, the 2006 El Niño didn't make it to 2007.

So where do we go from here?. For at least a few days
the storm track has shifted north. It appears the GWO might be starting an orbit that
will take it farther into the El Niño side of the phase space. Several MJO forecasts
show the next MJO cycle shortcutting it's orbit back into the Western Pacific. In
the 6-10 day period, the GEFS ensemble MJO forecast indicates enhancement of equatorial
convection around 90E, and suppression (by the MJO contribution) of El Niño convection
near the dateline. This could modify any short term response of the El Niño signal
and the GWO, once again reducing AAM.

Below are the GWO phase plots for two El Niños with ONI
and MEI values comparable to the current El Niño. In the 1986-87
El Niño, November to March AAM averaged 0.02, and it wasn't until February that
the GWO climbed out of the AAM doldrums. That water year Los Angeles recorded 7.66
inches of rain. On the other hand, in the 1994-95
El Niño, November to March AAM averaged 0.76. In mid December the GWO began to
reflect an ocean-atmosphere coupled El Niño response, and Los Angeles went on to record
24.35 inches of rain for the water year. At the moment it looks like Southern California
might not be as dry as 1986-87, but probably not as wet as 1994-95. We'll see!

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Southern California El Nino Impacts and the Global Wind Oscillationhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,98900d49-9d27-4fb5-babe-a5532939249d.aspxhttp://www.sierraphotography.com/wxnotes/SouthernCaliforniaElNinoImpactsAndTheGlobalWindOscillation.aspx
Wed, 16 Dec 2009 21:40:43 GMT
<p>
</p>
<table border="0">
<tbody>
<tr valign="top">
<td valign="top" nowrap="">
<center>
<p>
<a href="#"> <img onclick="MM_openBrWindow('wxdata0910/AHPSPrecip7Day121509_12zb.jpg','','resizable=yes,width=626,height=371');return false;" border="0" alt="AHPS Observed Precipitation For 7-days Ending 12/15/09 at 4:00 a.m. PST" src="wxdata0910/AHPSPrecip7Day121509_12zc.jpg" width="250" height="186" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">AHPS Observed Precipitation<br />
For 7-days Ending 12/15/09 at 4:00 a.m. PST</span>
</p>
</center>
</td>
<td valign="top">
<p>
<span class="dropcap">F</span>ollowing several weeks of dry weather, a shift to a
wetter pattern brought much needed rain and snow to California this past week. The
pattern change was apparently induced by MJO enhancement of El Niño convection in
the equatorial Pacific.
</p>
<p>
<span class="dropcap">D</span>owntown Los Angeles recorded 1.78 inches of rain from
Thursday to Sunday, bringing the water year total to 4.81 inches. This is about 2.20
inches above normal for the date. Rainfall totals generally ranged from 2 to 4 inches
in the basin and valleys, and 2 to 6 inches in the mountains. Here's an <a href="wxdata0910/PNSLOX121309_1031PST.pdf" target="_blank">archived
copy of a NWS Public Information Statement</a> with rainfall totals from around the
area.
</p>
</td>
</tr>
<tr valign="top">
<td valign="top" colspan="2">
<p>
<span class="dropcap">W</span>ill the current El Niño produce the expected seasonal
impacts in Southern California? A new tool that can help gain some insight into the
linkage of climate and weather is the <a href="http://www.esrl.noaa.gov/psd/map/clim/gsdm.composites.shtml" target="_blank">Global
Wind Oscillation</a> (GWO) phase space plot. Ed Berry repeatedly demonstrated the
usefulness of this tool in his blog <a href="http://weatherclimatelink.blogspot.com/" target="_blank">Atmospheric
Insights</a>. Although the blog has been discontinued, its content remains a valuable
resource.
</p>
<p>
<span class="dropcap">T</span>he GWO is a recurring subseasonal phenomenon that involves
the transport and interchange of momentum in the earth-atmosphere system. It encompasses
the MJO and occurs on a similar timescale. Analogous to the MJO phase space plot,
but based on a framework of atmospheric angular momentum (AAM), the GWO phase space
plot is a measure global relative atmospheric angular momentum and it's tendency.
For details, see <a href="http://www.esrl.noaa.gov/psd/map/clim/wb08_revised_final.pdf" target="_blank">Weickmann
&amp; Berry, 2008</a>.
</p>
<p>
<span class="dropcap">R</span>elative AAM is generally positive during an El Niño
and negative during a La Nina. Relative AAM is <a href="wxdata0910/CorrUSPrecip_AAM.gif" target="_blank">correlated
with rain season precipitation in Southern California</a>*, and can be helpful in
assessing potential El Niño impacts. The following November to March GWO phase plots
show the distinctly different behavior of the GWO during the <a href="wxdata0910/gwo_110197_033198b.jpg" target="_blank">strong
El Niño of 1997-98</a>, and the <a href="wxdata0910/gwo_110173_033174b.jpg" target="_blank">strong
La Nina of 1973-74</a>:
</p>
<table border="0" cellspacing="5" cellpadding="5" width="450" align="center">
<tbody>
<tr align="middle">
<td align="middle">
GWO El Niño 1997-1998</td>
<td align="middle">
GWO La Niña 1973-1974</td>
</tr>
<tr>
<td align="middle">
<a href="#"> <img onclick="MM_openBrWindow('wxdata0910/gwo_110197_033198b.jpg','','resizable=yes,width=708,height=591');return false;" border="0" alt="GWO El Nino 1997-1998" src="wxdata0910/gwo_110197_033198c.jpg" width="250" height="207" /> </a>
<br />
<span class="fontxxsmall">Click for larger image</span>
</td>
<td align="middle">
<a href="#"> <img onclick="MM_openBrWindow('wxdata0910/gwo_110173_033174b.jpg','','resizable=yes,width=708,height=591');return false;" border="0" alt="GWO La Nina 1973-1974" src="wxdata0910/gwo_110173_033174c.jpg" width="250" height="207" /> </a>
<br />
<span class="fontxxsmall">Click for larger image</span>
</td>
</tr>
</tbody>
</table>
<p>
<span class="dropcap">I</span>n a decade characterized by quirky El Niños, the El
Niño of 2009-10 has been acting like another odd one. From a Southern California perspective,
the concern has been that it might be like the El Niño of 2006-07 when Downtown Los
Angeles recorded only 3.21" of rain over the water year. In the early stages of the
El Niño of 2006 strong convection developed in the Indian Ocean during November, but
an MJO did not develop until a <a href="http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/ARCHIVE/PDF/mjo_evol-status-fcsts-20070115.pdf#page=6" target="_blank">second
round of Indian Ocean convection occurred in mid December.</a> Relative AAM remained
negative, and in terms of the atmosphere, the 2006 El Niño didn't make it to 2007.
</p>
<p>
<span class="dropcap">T</span>his year, Indian Ocean convection did spawn an MJO which <a href="http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/ARCHIVE/PDF/mjo_evol-status-fcsts-20091214.pdf#page=7" target="_blank">eventually
enhanced El Niño convection near the dateline</a>. Significant momentum was added
to the mid-latitudes of the Northern Hemisphere, energizing the westerlies and contributing
to the pattern change that resulted in our recent wet weather. However, the increase
in mid-latitude AAM has been mostly offset by negative anomalies at higher latitudes.
Following are the GWO phase space plots for the <a href="wxdata0910/gwo_110109_121409b.jpg" target="_blank">current
rain season to date</a>, and the <a href="wxdata0910/gwo_110106_033107b.jpg" target="_blank">quirky
El Niño of 2006-07</a>.
</p>
<p>
</p>
<table border="0" cellspacing="5" cellpadding="5" width="450" align="center">
<tbody>
<tr align="middle">
<td align="middle">
GWO El Niño 2009-2010</td>
<td align="middle">
GWO El Niño 2006-2007</td>
</tr>
<tr>
<td align="middle">
<a href="#"> <img onclick="MM_openBrWindow('wxdata0910/gwo_110109_121409b.jpg','','resizable=yes,width=708,height=591');return false;" border="0" alt="GWO El Nino 2009-2010" src="wxdata0910/gwo_110109_121409c.jpg" width="250" height="207" /> </a>
<br />
<span class="fontxxsmall">Click for larger image</span>
</td>
<td align="middle">
<a href="#"> <img onclick="MM_openBrWindow('wxdata0910/gwo_110106_033107b.jpg','','resizable=yes,width=708,height=591');return false;" border="0" alt="GWO El Nino 2006-2007" src="wxdata0910/gwo_110106_033107c.jpg" width="250" height="207" /> </a>
<br />
<span class="fontxxsmall">Click for larger image</span>
</td>
</tr>
</tbody>
</table>
<p>
<span class="dropcap">S</span>o where do we go from here?. For at least a few days
the storm track has shifted north. It appears the GWO might be starting an orbit that
will take it farther into the El Niño side of the phase space. Several MJO forecasts
show the next MJO cycle shortcutting it's orbit back into the Western Pacific. In
the 6-10 day period, the GEFS ensemble MJO forecast indicates enhancement of equatorial
convection around 90E, and suppression (by the MJO contribution) of El Niño convection
near the dateline. This could modify any short term response of the El Niño signal
and the GWO, once again reducing AAM.
</p>
<p>
<span class="dropcap">B</span>elow are the GWO phase plots for two El Niños with ONI
and MEI values comparable to the current El Niño. In the <a href="wxdata0910/gwo_110186_033187b.jpg" target="_blank">1986-87
El Niño</a>, November to March AAM averaged 0.02, and it wasn't until February that
the GWO climbed out of the AAM doldrums. That water year Los Angeles recorded 7.66
inches of rain. On the other hand, in the <a href="wxdata0910/gwo_110194_033195b.jpg" target="_blank">1994-95
El Niño</a>, November to March AAM averaged 0.76. In mid December the GWO began to
reflect an ocean-atmosphere coupled El Niño response, and Los Angeles went on to record
24.35 inches of rain for the water year. At the moment it looks like Southern California
might not be as dry as 1986-87, but probably not as wet as 1994-95. We'll see!
</p>
<table border="0" cellspacing="5" cellpadding="5" width="450" align="center">
<tbody>
<tr align="middle">
<td align="middle">
GWO El Niño 1986-1987</td>
<td align="middle">
GWO El Niño 1994-1995</td>
</tr>
<tr>
<td align="middle">
<a href="#"> <img onclick="MM_openBrWindow('wxdata0910/gwo_110186_033187b.jpg','','resizable=yes,width=708,height=591');return false;" border="0" alt="GWO El Nino 1986-1987" src="wxdata0910/gwo_110186_033187c.jpg" width="250" height="207" /> </a>
<br />
<span class="fontxxsmall">Click for larger image</span>
</td>
<td align="middle">
<a href="#"> <img onclick="MM_openBrWindow('wxdata0910/gwo_110194_033195b.jpg','','resizable=yes,width=708,height=591');return false;" border="0" alt="GWO El Nino 1994-1995" src="wxdata0910/gwo_110194_033195c.jpg" width="250" height="207" /> </a>
<br />
<span class="fontxxsmall">Click for larger image</span>
</td>
</tr>
</tbody>
</table>
<p>
*1958-2008 Precipitation/AAM correlation plot generated using <a href="http://www.esrl.noaa.gov/psd/data/usclimdivs/correlation/" target="_blank">US
Climate Division Dataset Seasonal Correlation Page</a>.
</p>
<p>
<span class="dropcap">M</span>ore information concerning Southern California weather
can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
<br />
</p>
</td>
</tr>
</tbody>
</table>
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<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)La NinaMadden-Julian Oscillation (MJO)weatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=021223c2-9a58-4c7d-999a-7548f55e7d72http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,021223c2-9a58-4c7d-999a-7548f55e7d72.aspxGary Valle

AHPS Observed Precipitation
For 30 days Ending 11/20/09

Drier than average weather in the Southwestern U.S.,
and wet weather in the Pacific Northwest in recent weeks has some folks wondering
if the 2009-2010 El Niño is going to be another one of the quirky, underachieving
El Niños we've been seeing this decade.

For much of September and October, the primary area of equatorial
convection in the Eastern Hemisphere was in the Central Pacific, just west of
the dateline. Convection was suppressed in the Indian Ocean. Such a pattern is consistent
with El Niño.

Enhanced convection centered at about 160E in early October
may have helped to extend the Pacific jet following an East Asian mountain torque
event around October 5. This in turn may have contributed to an atmospheric river
precipitation event in California October 13-14, 2009.

At that time it looked like we might finally be off and
running with a "real" El Niño event. Particularly because during October equatorial
Pacific SSTs and heat
content anomalies increased dramatically. Theses increases were the result of
of a strong Westerly
Wind Burst (WWB), an associated downwelling Kelvin wave, and diminished tradewinds,

However -- and I think I hear Ed Berry's Rottweiler growling
-- beginning in mid October, strong convection developed in the Indian Ocean. This
essentially neutralized El Niño, and perhaps contributed to the La Nina like precipitation
pattern we've been experiencing along the west coast of the U.S.

Indicative of the ocean-atmosphere issues, relative Atmospheric
Angular Momentum (AAM) has been negative since early September, and the Global
Wind Oscillation (GWO) has remained on the La Nina side of the GWO phase space.

Does this mean we've had an El Niño false alarm?

I wouldn't put away my rain gear just yet. Although November
rainfall for Downtown Los Angeles is about 0.6 inch below normal, we usually only
get about an inch of rain in November. And don't forget, because of the big storm
in October, we are still about 0.6 inch ABOVE normal rainfall for the water year.

Update November 24, 2009. Current equatorial heat content anomalies are about
the same as in 2006, not greater. See this composite
TAO/TRITON section plot comparing equatorial heat content in 2006 and 2009.

And there are some positive signs. Equatorial Pacific
SST and heat content anomalies are much greater than in the short-lived 2006 El Niño,
and are more along the lines of those observed in the 2002-2003 El Niño. In addition,
a strong MJO has developed. It has remained coherent, and is propagating
eastward into the Western Pacific. It already appears to be helping to enhance
convection in the Western and Central Pacific, and could kick-start the El Niño engine
over the next week or two. We'll see!

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
El Nino False Alarm?http://www.sierraphotography.com/wxnotes/PermaLink,guid,021223c2-9a58-4c7d-999a-7548f55e7d72.aspxhttp://www.sierraphotography.com/wxnotes/ElNinoFalseAlarm.aspx
Fri, 20 Nov 2009 15:32:56 GMT
<p>
</p>
<table border="0">
<tbody>
<tr valign="top">
<td valign="top" nowrap="">
<center>
<p>
<a href="#"> <img onclick="MM_openBrWindow('wxdata0910/AHPSPrecip30DayDepart112009_12zb.jpg','','resizable=yes,width=641,height=387');return false;" border="0" alt="AHPS Observed Precipitation For 30 days Ending 11/20/09" src="wxdata0910/AHPSPrecip30DayDepart112009_12zc.jpg" width="250" height="166" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">AHPS Observed Precipitation<br />
For 30 days Ending 11/20/09</span>
</p>
</center>
</td>
<td valign="top">
<p>
<span class="dropcap">D</span>rier than average weather in the Southwestern U.S.,
and wet weather in the Pacific Northwest in recent weeks has some folks wondering
if the 2009-2010 El Niño is going to be another one of the quirky, underachieving
El Niños we've been seeing this decade.
</p>
<p>
<span class="dropcap">F</span>or much of September and October, the primary area of <a href="wxdata0910/cpc_filteredOLRAnom111409b.gif" target="_blank">equatorial
convection</a> in the Eastern Hemisphere was in the Central Pacific, just west of
the dateline. Convection was suppressed in the Indian Ocean. Such a pattern is consistent
with El Niño.
</p>
</td>
</tr>
<tr valign="top">
<td valign="top" colspan="2">
<p>
<span class="dropcap">E</span>nhanced convection centered at about 160E in early October
may have helped to extend the Pacific jet following an East Asian mountain torque
event around October 5. This in turn may have contributed to an atmospheric river
precipitation event in California October 13-14, 2009.
</p>
<p>
<span class="dropcap">A</span>t that time it looked like we might finally be off and
running with a "real" El Niño event. Particularly because during October <a href="wxdata0910/SST_7day111109b.png" target="_blank">equatorial
Pacific SSTs</a> and <a href="wxdata0910/cpc_heatcontent110909b.gif" target="_blank">heat
content</a> anomalies increased dramatically. Theses increases were the result of
of a <a href="wxdata0910/cdas_850hPaWindAnom111709b.gif" target="_blank">strong Westerly
Wind Burst</a> (WWB), an associated downwelling Kelvin wave, and diminished tradewinds,
</p>
<p>
<span class="dropcap">H</span>owever -- and I think I hear Ed Berry's Rottweiler growling
-- beginning in mid October, strong convection developed in the Indian Ocean. This
essentially neutralized El Niño, and perhaps contributed to the La Nina like precipitation
pattern we've been experiencing along the west coast of the U.S.
</p>
<p>
<span class="dropcap">I</span>ndicative of the ocean-atmosphere issues, relative Atmospheric
Angular Momentum (AAM) has been negative since early September, and the <a href="wxdata0910/gwo_90d111609b.gif" target="_blank">Global
Wind Oscillation</a> (GWO) has remained on the La Nina side of the GWO phase space.
</p>
<p>
<span class="dropcap">D</span>oes this mean we've had an El Niño false alarm?
</p>
<p>
<span class="dropcap">I</span> wouldn't put away my rain gear just yet. Although November
rainfall for Downtown Los Angeles is about 0.6 inch below normal, we usually only
get about an inch of rain in November. And don't forget, because of the big storm
in October, we are still about 0.6 inch ABOVE normal rainfall for the water year.
</p>
<p>
<i>Update November 24, 2009</i>. Current equatorial heat content anomalies are about
the same as in 2006, not greater. See this <a href="wxdata0910/TAO_5DayHeatContentSection112306_09b.gif">composite
TAO/TRITON section plot</a> comparing equatorial heat content in 2006 and 2009.
</p>
<p>
<span class="dropcap">A</span>nd there are some positive signs. Equatorial Pacific
SST and heat content anomalies are much greater than in the short-lived 2006 El Niño,
and are more along the lines of those observed in the 2002-2003 El Niño. In addition,
a strong MJO has developed. It has remained coherent, and is <a href="wxdata0910/MJO40d111909b.gif" target="_blank">propagating
eastward into the Western Pacific</a>. It already appears to be helping to enhance
convection in the Western and Central Pacific, and could kick-start the El Niño engine
over the next week or two. We'll see!
</p>
<p>
<span class="dropcap">M</span>ore information concerning Southern California weather
can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
<br />
</p>
</td>
</tr>
</tbody>
</table>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=021223c2-9a58-4c7d-999a-7548f55e7d72" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)Los Angeles rainfallweatherWesterly Wind Burst (WWB)http://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=609d2c0f-4822-48ff-8724-4b77c10b1a6dhttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,609d2c0f-4822-48ff-8724-4b77c10b1a6d.aspxGary Valle

GOES-11 IR Satellite Image
Tuesday, Sept. 29, 2009 1:30 p.m. PDT

The frontal band associated with the first Pacific upper
level low system and trough of Autumn 2009 is producing some
showers in Central California. Some snow showers could occur at the higher elevations
of the Sierra. A strong onshore flow has dramatically cooled temperatures throughout
the state.

Today's cool temps are a welcome respite from several
days of hot weather. Wednesday and Thursday of last week, Downtown Los Angeles (USC)
recorded a high of 100°F; and Saturday, Woodland Hills (Pierce College) reported a
high of 107°F. Temperatures are expected to rebound Wednesday, Thursday and Friday,
but are forecast to cool again over the weekend.

Similar to what occurred in July there has been little
change in equatorial Pacific SST anomalies, the Southern Oscillation Index (SOI) has
switched from negative to positive, the Aug-Sep Multivariate
ENSO Index (MEI) value is not expected to significantly increase, and the Global
Wind Oscillation (GWO) has dropped its orbit to a lower relative AAM state.

On the plus side, a large area of enhanced convection
has redeveloped in the West Central Pacific from about 150E to the dateline, and another
of a series of Westerly Wind Bursts (WWB) is occurring -- the strongest observed so
far during this ENSO transition. This WWB will likely be followed by another eastward
propagating downwelling Kelvin wave, which could help increase upper-ocean heat content
anomalies in the equatorial Pacific.

Moderate El Niños come in many flavors and
have varying impacts. Under the guise of such El Niños Los Angeles experienced
its second wettest water year on record in 2004-2005, when 37.25 inches of rain was
recorded; then in 2006-2007 had its driest water year on record, when only 3.21" was
recorded.

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
First Autumn Cold Front. Mixed El Nino Signals Continue.http://www.sierraphotography.com/wxnotes/PermaLink,guid,609d2c0f-4822-48ff-8724-4b77c10b1a6d.aspxhttp://www.sierraphotography.com/wxnotes/FirstAutumnColdFrontMixedElNinoSignalsContinue.aspx
Tue, 29 Sep 2009 14:54:15 GMT
<p>
</p>
<table border="0">
<tbody>
<tr valign="top">
<td valign="top" nowrap="">
<center>
<p>
<a href="#"> <img onclick="MM_openBrWindow('wxdata0910/goes11ir092909_2030zb.gif','','resizable=yes,width=660,height=500');return false;" border="0" alt="GOES-11 IR Satellite Image Tuesday, Sept. 29, 2009 1:30 p.m. PDT" src="wxdata0910/goes11ir092909_2030zc.gif" width="250" height="188" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">GOES-11 IR Satellite Image<br />
Tuesday, Sept. 29, 2009 1:30 p.m. PDT</span>
</p>
</center>
</td>
<td valign="top">
<p>
<span class="dropcap">T</span>he frontal band associated with the first Pacific upper
level low system and trough of Autumn 2009 is producing <a href="wxdata0910/wsicompradar_092909_2015zb.gif" target="_blank">some
showers in Central California</a>. Some snow showers could occur at the higher elevations
of the Sierra. A strong onshore flow has dramatically cooled temperatures throughout
the state.
</p>
<p>
<span class="dropcap">T</span>oday's cool temps are a welcome respite from several
days of hot weather. Wednesday and Thursday of last week, Downtown Los Angeles (USC)
recorded a high of 100°F; and Saturday, Woodland Hills (Pierce College) reported a
high of 107°F. Temperatures are expected to rebound Wednesday, Thursday and Friday,
but are forecast to cool again over the weekend.
</p>
</td>
</tr>
<tr valign="top">
<td valign="top" colspan="2">
<p>
<span class="dropcap">S</span>imilar to what occurred in July there has been little
change in equatorial Pacific SST anomalies, the Southern Oscillation Index (SOI) has
switched from negative to positive, the Aug-Sep <a href="http://www.cdc.noaa.gov/people/klaus.wolter/MEI/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) value is not expected to significantly increase, and the Global
Wind Oscillation (GWO) has dropped its orbit to a lower relative AAM state.
</p>
<p>
<span class="dropcap">O</span>n the plus side, a large area of enhanced convection
has redeveloped in the West Central Pacific from about 150E to the dateline, and another
of a series of Westerly Wind Bursts (WWB) is occurring -- the strongest observed so
far during this ENSO transition. This WWB will likely be followed by another eastward
propagating downwelling Kelvin wave, which could help increase upper-ocean heat content
anomalies in the equatorial Pacific.
</p>
<p>
<span class="dropcap">M</span>oderate El Ni<span>ñ</span>os come in many flavors and
have varying impacts. Under the guise of such El Ni<span>ñ</span>os Los Angeles experienced
its second wettest water year on record in 2004-2005, when 37.25 inches of rain was
recorded; then in 2006-2007 had its driest water year on record, when only 3.21" was
recorded.
</p>
<p>
<span class="dropcap">M</span>ore information concerning Southern California weather
can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
<br />
</p>
</td>
</tr>
</tbody>
</table>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=609d2c0f-4822-48ff-8724-4b77c10b1a6d" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)Los Angeles temperatureMultivariate ENSO Index (MEI)Southern Oscillation Index (SOI)weatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=1fcd7088-d1f1-42ca-aae2-3ecc44866e42http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,1fcd7088-d1f1-42ca-aae2-3ecc44866e42.aspxGary Valle

Global Wind Oscillation Phase Space
May 7, 2009 vs August 4, 2009

After spending the last week of May and most of June
on the positive relative AAM (El Niño) side of the Global Wind Oscillation (GWO) phase
space, the GWO slipped back into negative relative AAM territory the last week of
June and stayed there most of July. Following the lead of the atmosphere, development
of the current El Niño also slowed in July.

However, during July, enhanced tropical convection shifted
from the western Indian Ocean to the west central Pacific, extending from about 140E
to the dateline. This was followed by the development of a strong
Westerly Wind Burst (WWB) in the western Pacific. Coincident with the WWB was
a dramatic reduction in the SOI, and an an orbit of the GWO to a somewhat higher global
relative AAM state. These events are consistent with a developing El Niño.

According to the El
Niño/Southern Oscillation (ENSO) Diagnostic Discussion issued August 6 by the
Climate Prediction Center/NCEP/NWS, "current conditions and model forecasts favor
the continued development of a weak-to-moderate strength El Niño into the Northern
Hemisphere Fall 2009, with the likelihood of at least a moderate strength El Niño
(3-month Niño-3.4 SST index of +1.0°C or greater) during the Northern Hemisphere Winter
2009-10."

How often are Summer temps hotter in Seattle than the
San Fernando Valley? From July 26 to August 3, 2009, the Seattle area suffered through
a heat wave that broke numerous records, including several "all-time" temperature
records. On July 29, 2009 Sea-Tac reached 103°F, Bellingham 96°F, and Seattle WFO
(Sandpoint) 105°F, the highest temperature ever recorded at these stations.

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
El Nino Development Slows. Seattle Swelters.http://www.sierraphotography.com/wxnotes/PermaLink,guid,1fcd7088-d1f1-42ca-aae2-3ecc44866e42.aspxhttp://www.sierraphotography.com/wxnotes/ElNinoDevelopmentSlowsSeattleSwelters.aspx
Thu, 06 Aug 2009 15:14:57 GMT
<p>
</p>
<table border="0">
<tbody>
<tr valign="top">
<td valign="top" nowrap="">
<center>
<p>
<a href="#"> <img onclick="MM_openBrWindow('wxdata0910/gwo_90d080409b.gif','','resizable=yes,width=820,height=820');return false;" border="0" alt="Global Wind Oscillation Phase Space - May 7, 2009 vs August 4, 2009" src="wxdata0910/gwo_90d080409c.gif" width="250" height="250" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">Global Wind Oscillation Phase Space<br />
May 7, 2009 vs August 4, 2009</span>
</p>
</center>
</td>
<td valign="top">
<p>
<span class="dropcap">A</span>fter spending the last week of May and most of June
on the positive relative AAM (El Niño) side of the Global Wind Oscillation (GWO) phase
space, the GWO slipped back into negative relative AAM territory the last week of
June and stayed there most of July. Following the lead of the atmosphere, development
of the current El Niño also slowed in July.
</p>
<p>
<span class="dropcap">D</span>uring July there was little change in <a href="wxdata0910/NinoIndices0809b.gif" target="_blank">equatorial
Pacific SST anomalies</a>; the <a href="wxdata0910/soi30_080409b.png" target="_blank">Southern
Oscillation Index</a> (SOI) became strongly positive; and the June-July <a href="http://www.cdc.noaa.gov/people/klaus.wolter/MEI/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) value, reported August 5, increased by only 0.05.
</p>
<p>
<span class="dropcap">H</span>owever, during July, enhanced tropical convection shifted
from the western Indian Ocean to the west central Pacific, extending from about 140E
to the dateline. This was followed by the development of a <a href="wxdata0910/CPC_CDAS850hPaWindAnomb.gif" target="_blank">strong
Westerly Wind Burst</a> (WWB) in the western Pacific. Coincident with the WWB was
a dramatic reduction in the SOI, and an an orbit of the GWO to a somewhat higher global
relative AAM state. These events are consistent with a developing El Niño.
</p>
</td>
</tr>
<tr valign="top">
<td valign="top" colspan="2">
<p>
<span class="dropcap">A</span>ccording to the <a href="wxdata0910/ensodisc080609.pdf" target="_blank">El
Niño/Southern Oscillation (ENSO) Diagnostic Discussion issued August 6</a> by the
Climate Prediction Center/NCEP/NWS, "current conditions and model forecasts favor
the continued development of a weak-to-moderate strength El Niño into the Northern
Hemisphere Fall 2009, with the likelihood of at least a moderate strength El Niño
(3-month Niño-3.4 SST index of +1.0°C or greater) during the Northern Hemisphere Winter
2009-10."
</p>
<p>
<span class="dropcap">H</span>ow often are Summer temps hotter in Seattle than the
San Fernando Valley? From July 26 to August 3, 2009, the Seattle area suffered through
a heat wave that broke numerous records, including several "all-time" temperature
records. On July 29, 2009 Sea-Tac reached 103°F, Bellingham 96°F, and Seattle WFO
(Sandpoint) 105°F, the highest temperature ever recorded at these stations.
</p>
<p>
<span class="dropcap">M</span>ore information concerning Southern California weather
can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
<br />
</p>
</td>
</tr>
</tbody>
</table>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=1fcd7088-d1f1-42ca-aae2-3ecc44866e42" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)Multivariate ENSO Index (MEI)Southern Oscillation Index (SOI)weatherWesterly Wind Burst (WWB)http://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=827fa621-9bdb-47db-aced-f0a79a67014ahttp://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,827fa621-9bdb-47db-aced-f0a79a67014a.aspxGary Valle

Downtown Los Angeles (USC) ended the water year on June
30th having recorded 9.08 inches of rain, which is 6.06 inches below the 1971-2000
norm of 15.14 inches. Some additional water year rainfall totals:

Santa Barbara

10.12"

60%

Camarillo

6.61"

42%

Burbank

10.65"

61%

Palmdale

5.24"

71%

Sandberg

10.68"

85%

According to the El
Nino/Southern Oscillation (ENSO) Diagnostic Discussion issued July 9 by the Climate
Prediction Center/NCEP/NWS, "During June 2009, conditions across the equatorial Pacific
Ocean transitioned from ENSO-neutral to El Niño conditions." According to the report,
El Nino conditions are expected to continue to develop, and last through the NH Winter.

The May-June Multivariate
ENSO Index (MEI) value, reported July 6, has increased by 0.51 to +0.85. As was
the case last month, the 3-month rise of the MEI (since February-March) is the 4th
highest on record for this time of year, and was last exceeded by the strong El Niño
of 1997. According to the MEI's originator, Dr. Klaus Wolter, "the combination of
already border-line moderate El Niño conditions along with such a big rise in the
MEI at this time of year has always been followed by continued El Niño conditions
through the remainder of the calendar year, at least in the modern MEI record (since
1950)."

However, as the truncated 2006-07 El Niño event demonstrates,
an El Niño is more than just warm Pacific equatorial SSTs. Through complex forcing
and feedback mechanisms, the atmosphere and oceans have to cooperate on a global scale.
As climate scientist Ed Berry cautions in his July
3rd Atmospheric Insights post, "Should total AAM departures become comparable
to that observed during this past January and February, my concerns of an El-Nino
'false alarm' for the weather-climate dynamical system will be significantly raised."

Generally speaking, the momentum of the atmosphere increases
when there is an El Niño, and decreases during a La Niña. Over the past 40 days the Global
Wind Oscillation (GWO) has retreated from the higher AAM (El Niño) side of the
GWO phase space to the lower AAM (La Niña) side. One concern is that two areas of
tropical forcing (Indian Ocean and Pacific) may interact in such a way as to quash
the El Niño engine. We'll see!

Closer to home, although temps in Southern California
have recently been more seasonable, particularly in the Valleys, the last time the
average daily temperature in Downtown Los Angeles was above normal was back on May
21 -- 48 days ago.

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
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Thu, 09 Jul 2009 15:20:43 GMT
<p>
</p>
<table border="0">
<tbody>
<tr valign="top">
<td valign="top" nowrap="">
<center>
<p>
<a href="#"> <img onclick="MM_openBrWindow('wxdata0910/NOAA_NESDIS_SSTanom070308_070209.gif','','resizable=yes,width=620,height=347');return false;" border="0" alt="Click for Animation" src="wxdata0910/GlobalSSTanomJul08Jul09c.jpg" width="250" height="294" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">NOAA/NESDIS 50km Global SST Anomaly<br />
July 3, 2008 vs July 2, 2009<br />
<a onclick="MM_openBrWindow('wxdata0910/NOAA_NESDIS_SSTanom070308_070209.gif','','resizable=yes,width=620,height=347');return false;" href="#">Click
for Animation</a></span>
</p>
</center>
</td>
<td valign="top">
<p>
<span class="wxTitle">Los Angeles Temps Continue Below Normal. </span>
</p>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) ended the water year on June
30th having recorded 9.08 inches of rain, which is 6.06 inches below the 1971-2000
norm of 15.14 inches. Some additional water year rainfall totals:
</p>
<table border="1" cellspacing="0" cellpadding="2" align="center">
<tbody>
<tr>
<td>
Santa Barbara</td>
<td>
10.12"</td>
<td>
60%</td>
</tr>
<tr>
<td>
Camarillo</td>
<td>
6.61"</td>
<td>
42%</td>
</tr>
<tr>
<td>
Burbank</td>
<td>
10.65"</td>
<td>
61%</td>
</tr>
<tr>
<td>
Palmdale</td>
<td>
5.24"</td>
<td>
71%</td>
</tr>
<tr>
<td>
Sandberg</td>
<td>
10.68"</td>
<td>
85%</td>
</tr>
</tbody>
</table>
<p>
<span class="dropcap">A</span>ccording to the <a href="wxdata0910/ensodisc070909.pdf" target="_blank">El
Nino/Southern Oscillation (ENSO) Diagnostic Discussion issued July 9</a> by the Climate
Prediction Center/NCEP/NWS, "During June 2009, conditions across the equatorial Pacific
Ocean transitioned from ENSO-neutral to El Niño conditions." According to the report,
El Nino conditions are expected to continue to develop, and last through the NH Winter.
</p>
</td>
</tr>
<tr valign="top">
<td valign="top" colspan="2">
<p>
<span class="dropcap">T</span>he May-June <a href="http://www.cdc.noaa.gov/people/klaus.wolter/MEI/index.html" target="_blank">Multivariate
ENSO Index</a> (MEI) value, reported July 6, has increased by 0.51 to +0.85. As was
the case last month, the 3-month rise of the MEI (since February-March) is the 4th
highest on record for this time of year, and was last exceeded by the strong El Niño
of 1997. According to the MEI's originator, Dr. Klaus Wolter, "the combination of
already border-line moderate El Niño conditions along with such a big rise in the
MEI at this time of year has always been followed by continued El Niño conditions
through the remainder of the calendar year, at least in the modern MEI record (since
1950)."
</p>
<p>
<span class="dropcap">H</span>owever, as the truncated 2006-07 El Niño event demonstrates,
an El Niño is more than just warm Pacific equatorial SSTs. Through complex forcing
and feedback mechanisms, the atmosphere and oceans have to cooperate on a global scale.
As climate scientist Ed Berry cautions in his <a href="http://weatherclimatelink.blogspot.com/2009/07/brief-update-on-bearish-atmosphere.html" target="_blank">July
3rd Atmospheric Insights post</a>, "Should total AAM departures become comparable
to that observed during this past January and February, my concerns of an El-Nino
'false alarm' for the weather-climate dynamical system will be significantly raised."
</p>
<p>
<span class="dropcap">G</span>enerally speaking, the momentum of the atmosphere increases
when there is an El Niño, and decreases during a La Niña. Over the past 40 days the <a onclick="MM_openBrWindow('wxdata0910/gwo_40d_070709b.gif','','resizable=yes,width=820,height=820');return false;" href="#">Global
Wind Oscillation</a> (GWO) has retreated from the higher AAM (El Niño) side of the
GWO phase space to the lower AAM (La Niña) side. One concern is that two areas of
tropical forcing (Indian Ocean and Pacific) may interact in such a way as to quash
the El Niño engine. We'll see!
</p>
<p>
<span class="dropcap">C</span>loser to home, although temps in Southern California
have recently been more seasonable, particularly in the Valleys, the last time the
average daily temperature in Downtown Los Angeles was above normal was back on May
21 -- 48 days ago.
</p>
<p>
<span class="dropcap">M</span>ore information concerning Southern California weather
can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
<br />
</p>
</td>
</tr>
</tbody>
</table>
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<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)Los Angeles rainfallMultivariate ENSO Index (MEI)weatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=39334a12-2b1f-4866-b2b9-db9805a8abb4http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,39334a12-2b1f-4866-b2b9-db9805a8abb4.aspxGary Valle

Aqua Modis Satellite Image
June 3, 2009 2:15 p.m. PDT

Unusual weather for June. Not so much that there were
thunderstorms, but that the thunderstorms were in part the result of an unseasonably
strong jet embedded in the base of an offshore upper level low.

It's a bit of a stretch, but an argument could be made
that these storms were a calling card of an increasingly energetic atmosphere, and
a developing El Niño.

Downtown Los Angeles (USC) recorded a total of 0.02 inch
of rain Wednesday. The rainfall increased the water year precipitation total for Los
Angeles to 8.95 inches, which is 6.16 inches below normal.

It's not often that a trace of rainfall sets a record,
but that was the case at Camarillo Airport and Palmdale, which had not previously
recorded precipitation on June 3. The 0.03 inches recorded at Sandberg was also a
record. Here's a CNRFC graphic with some 24
hour rainfall totals in Los Angeles County.

Several factors point to an increased probability of
El Niño conditions developing over the next few months. Among them, Equatorial Pacific
SSTs have increased, and the subsurface heat content is the highest it's been since
the El Niño of 2006-07.

But as the short-lived 2006-07 El Niño event demonstrates,
an El Niño is more than just warm Pacific equatorial SSTs. Through complex forcing
and feedback mechanisms, the atmosphere and oceans have to cooperate on a global scale.
Generally speaking the momentum of the atmosphere increases when there is an El Niño,
and decreases during a La Nina.

And it looks like the atmospheric momentum may be increasing.
Orbits of the Global
Wind Oscillation (GWO), a measure of atmospheric momentum, have been shifting
upward, in the direction of more energetic values usually associated with an El Niño.

However, an El Niño is not a done deal. The climate system
is just leaning in that direction. As climate scientist Klaus Wolter has previously
pointed out, in a similar situation in 1973-1975, the climate fell back into a La
Niña for another year. But at this point it appears we may be diverging from that
analog case. (See June 6 Weathernotes.) We'll see!

Update 06/05/09. Unseasonably strong 110+ kt jet overhead as upper
low center moves onshore in Central California. At 7:15 this morning, Intellicast
composite radar showed most of the shower activity occurring to the north of Los
Angeles, but there has been scattered showers in the Los Angeles area as well, with
measurable rain recorded at a number of stations. Here's an archived copy of a NWS
Public Information Statement with some preliminary
rainfall totals as of 5:00 p.m.

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Late Season Thunderstorms an El Nino Calling Card?http://www.sierraphotography.com/wxnotes/PermaLink,guid,39334a12-2b1f-4866-b2b9-db9805a8abb4.aspxhttp://www.sierraphotography.com/wxnotes/LateSeasonThunderstormsAnElNinoCallingCard.aspx
Thu, 04 Jun 2009 15:28:22 GMT
<p>
</p>
<table border="0">
<tbody>
<tr valign="top">
<td valign="top" nowrap="">
<center>
<p>
<a href="#"> <img onclick="MM_openBrWindow('wxdata0809/AquaModisWest_Calif_South060309_2115b.jpg','','resizable=yes,width=820,height=820');return false;" border="0" alt="Aqua Modis Satellite Image June 3, 2009 2:15 p.m. PDT" src="wxdata0809/AquaModisWest_Calif_South060309_2115c.jpg" width="250" height="178" /> </a> <img alt="Click" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">Aqua Modis Satellite Image<br />
June 3, 2009 2:15 p.m. PDT</span>
</p>
</center>
</td>
<td valign="top">
<p>
<span class="dropcap">U</span>nusual weather for June. Not so much that there were
thunderstorms, but that the thunderstorms were in part the result of an unseasonably
strong jet embedded in the base of an offshore upper level low.
</p>
<p>
<span class="dropcap">I</span>t's a bit of a stretch, but an argument could be made
that these storms were a calling card of an increasingly energetic atmosphere, and
a developing El Niño.
</p>
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) recorded a total of 0.02 inch
of rain Wednesday. The rainfall increased the water year precipitation total for Los
Angeles to 8.95 inches, which is 6.16 inches below normal.
</p>
</td>
</tr>
<tr valign="top">
<td valign="top" colspan="2">
<p>
<span class="dropcap">I</span>t's not often that a trace of rainfall sets a record,
but that was the case at Camarillo Airport and Palmdale, which had not previously
recorded precipitation on June 3. The 0.03 inches recorded at Sandberg was also a
record. Here's a CNRFC graphic with some <a onclick="MM_openBrWindow('wxdata0809/CNRFC_la_060409_precip.png','','resizable=yes,width=640,height=826');return false;" href="#" target="_blank">24
hour rainfall totals in Los Angeles County</a>.
</p>
<p>
<span class="dropcap">S</span>everal factors point to an increased probability of
El Niño conditions developing over the next few months. Among them, Equatorial Pacific
SSTs have increased, and the subsurface heat content is the highest it's been since
the El Niño of 2006-07.
</p>
<p>
<span class="dropcap">B</span>ut as the short-lived 2006-07 El Niño event demonstrates,
an El Niño is more than just warm Pacific equatorial SSTs. Through complex forcing
and feedback mechanisms, the atmosphere and oceans have to cooperate on a global scale.
Generally speaking the momentum of the atmosphere increases when there is an El Niño,
and decreases during a La Nina.
</p>
<p>
<span class="dropcap">A</span>nd it looks like the atmospheric momentum may be increasing.
Orbits of the <a href="http://www.cdc.noaa.gov/map/clim/gsdm.composites.shtml" target="_blank">Global
Wind Oscillation</a> (GWO), a measure of atmospheric momentum, have been shifting
upward, in the direction of more energetic values usually associated with an El Niño.
</p>
<p>
<span class="dropcap">H</span>owever, an El Niño is not a done deal. The climate system
is just leaning in that direction. As climate scientist Klaus Wolter has previously
pointed out, in a similar situation in 1973-1975, the climate fell back into a La
Niña for another year. But at this point it appears we may be diverging from that
analog case. (See June 6 Weathernotes.) We'll see!
</p>
<p>
<i>Update 06/05/09</i>. Unseasonably strong 110+ kt jet overhead as <a onclick="MM_openBrWindow('wxdata0809/goes11ir060509_1400zb.gif','','resizable=yes,width=660,height=500');return false;" href="#">upper
low center moves onshore</a> in Central California. At 7:15 this morning, <a onmouseover="MM_openBrWindow('wxdata0809/wsicompradar_060509_1415zb.gif','','resizable=yes,width=788,height=516');return false;" href="#">Intellicast
composite radar</a> showed most of the shower activity occurring to the north of Los
Angeles, but there has been scattered showers in the Los Angeles area as well, with
measurable rain recorded at a number of stations. Here's an archived copy of a NWS
Public Information Statement with some <a href="wxdata0809/PNSLOX060509_1725PDT.pdf" target="_blank">preliminary
rainfall totals</a> as of 5:00 p.m.
</p>
<p>
<span class="dropcap">M</span>ore information concerning Southern California weather
can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
<br />
</p>
</td>
</tr>
</tbody>
</table>
<img width="0" height="0" src="http://www.sierraphotography.com/wxnotes/aggbug.ashx?id=39334a12-2b1f-4866-b2b9-db9805a8abb4" />
<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateEl NinoGlobal Wind Oscillation (GWO)Los Angeles rainfallweatherhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=56ffc009-6dbe-4402-b844-704243831444http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,56ffc009-6dbe-4402-b844-704243831444.aspxGary Valle

Intellicast.com Composite Radar
May 1, 2009 6:15 p.m. PDT

An unseasonably strong, late season Pacific storm system
brought rain to much of California Friday and Saturday, including some areas of Southern
California.

Los Angeles basin and valley areas generally recorded
a trace of precipitation, but some stations in the Ventura mountains recorded as much
as 0.3 inch. Here is an archived copy of a NWS
Public Information Statement, with some precipitation totals from around the area.

Heavier rain occurred in Central California. A new rainfall
record for May 1 was set in Sacramento, and higher elevations of the Sierra received
about a foot of snow. Enhanced southwesterly, sub-tropical flow, and enhanced
convection associated with the phase 7 MJO may have contributed to the strength
of the system.

Downtown Los Angeles (USC) happened to be under the right
cloud yesterday, and recorded 0.02 inch of rain. There's a continuing chance of showers
in Southern California through the weekend. The area could use some rain. The last
storm to produce more than a couple tenths of inch of rain at Downtown Los Angeles
was back on February 24, 2008 -- more than eight months ago.

Last year, California's rain season might have been scripted
by Dr. Jekyll and Mr. Hyde. Lowland rain totals and the Sierra snowpack were well
above normal through the end of February, and then the spigot was turned off. The
storm track shifted north, and California had its driest March to May on record. (The March
29, 2008 post in Ed Berry's Atmospheric Insights blog describes the events that
may have led to and maintained this shift.)

Which rain season personality will emerge this Winter?
Earlier this year the equatorial Pacific tried to transition to El Nino, but the atmosphere
didn't cooperate. As measured by the Multivariate ENSO Index (MEI), the ENSO state
has returned to the weak La Nina threshold. And as measured by the Global Wind Oscillation
(GWO), an uncooperative atmosphere has continued to cycle through a La Nina base state.

This suggests a winter precipitation outlook with a La
Nina flavor -- similar to last year. This precipitation
map, generated by the ESRL-PSD Composite ENSO plots page, shows the mean November-March
precipitation for the U.S. during 9 La Niña events from 1948 to the present. The average
La Niña rainfall indicated for coastal Southern California is in the 7.0-10.5 inch
range. Last season's November-March rainfall in Downtown Los Angeles was about 12
inches.

Update 11/4/08. Here are the NWS Public Information Statements with preliminary
rainfall totals for the period from Friday
evening to Sunday morning, and from overnight
last night to 10:00 a.m. this morning. The current Climate Prediction Center 6-10
day and 8-14 Precipitation Outlooks project below normal rainfall for Southern California.
In Atmospheric
Insights, Ed Berry paints a scenario with an extended North Pacific Jet collapsing
into a strong western U.S. trough in the week 2-3 timeframe. We'll see!

More information concerning Southern California weather
can be found using our WEATHER LINKS page.

Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.
Halloween Showers? Winter Precipitation Outlook.http://www.sierraphotography.com/wxnotes/PermaLink,guid,e5a57982-f3fc-484a-be05-7270db824741.aspxhttp://www.sierraphotography.com/wxnotes/HalloweenShowersWinterPrecipitationOutlook.aspx
Sat, 01 Nov 2008 00:34:21 GMT
<p>
</p>
<table border="0">
<tbody>
<tr valign="top">
<td valign="top" nowrap="">
<center>
<p>
<a href="#"> <img onclick="MM_openBrWindow('wxdata0809/wsicompradar_103108_1630zb.gif','','resizable=yes,width=785,height=520');return false;" border="0" alt="Intellicast Composite Radar Friday, October 31, 2008 - 9:30 a.m. PDT" src="wxdata0809/wsicompradar_103108_1630zc.gif" width="250" height="161" /> </a> <img border="0" alt="Click!" src="images/click.gif" width="16" height="34" />
<br />
<span class="fontxxsmall">Intellicast Composite Radar<br />
Friday, October 31, 2008 - 9:30 a.m. PDT</span>
</p>
</center>
</td>
<td valign="top">
<p>
<span class="dropcap">D</span>owntown Los Angeles (USC) happened to be under the right
cloud yesterday, and recorded 0.02 inch of rain. There's a continuing chance of showers
in Southern California through the weekend. The area could use some rain. The last
storm to produce more than a couple tenths of inch of rain at Downtown Los Angeles
was back on February 24, 2008 -- more than eight months ago.
</p>
<p>
<span class="dropcap">L</span>ast year, California's rain season might have been scripted
by Dr. Jekyll and Mr. Hyde. Lowland rain totals and the Sierra snowpack were well
above normal through the end of February, and then the spigot was turned off. The
storm track shifted north, and California had its driest March to May on record. (The <a href="http://weatherclimatelink.blogspot.com/2008/03/bear-market-atmosphere.html" target="_blank">March
29, 2008 post</a> in Ed Berry's Atmospheric Insights blog describes the events that
may have led to and maintained this shift.)
</p>
</td>
</tr>
<tr valign="top">
<td valign="top" colspan="2">
<p>
<span class="dropcap">W</span>hich rain season personality will emerge this Winter?
Earlier this year the equatorial Pacific tried to transition to El Nino, but the atmosphere
didn't cooperate. As measured by the Multivariate ENSO Index (MEI), the ENSO state
has returned to the weak La Nina threshold. And as measured by the Global Wind Oscillation
(GWO), an uncooperative atmosphere has continued to cycle through a La Nina base state.
</p>
<p>
<span class="dropcap">T</span>his suggests a winter precipitation outlook with a La
Nina flavor -- similar to last year. This <a href="wxdata0708/ESRL_PSD_LaNinaComposite011008b.gif" target="_blank">precipitation
map</a>, generated by the ESRL-PSD Composite ENSO plots page, shows the mean November-March
precipitation for the U.S. during 9 La Niña events from 1948 to the present. The average
La Niña rainfall indicated for coastal Southern California is in the 7.0-10.5 inch
range. Last season's November-March rainfall in Downtown Los Angeles was about 12
inches.
</p>
<p>
<span class="dropcap">H</span>ere's the current <a href="wxdata0809/PrecipOutlookNDJ_101608b.gif" target="_blank">Nov-Dec-Jan
precipitation outlook</a> issued October 16 by the Climate Prediction Center. The
"EC" means an equal chance of below normal, near normal, or above normal precipitation.
The <a href="http://iri.columbia.edu/climate/forecast/net_asmt/2008/oct2008/NDJ09_NAm_pcp.html" target="_blank">IRI
Multi Model Seasonal Forecast for Nov-Dec-Jan</a> is similar. We'll see!
</p>
<p>
<i>Update 11/4/08</i>. Here are the NWS Public Information Statements with preliminary
rainfall totals for the period from <a href="wxdata0809/PNSLOX110208_1042PST.pdf" target="_blank">Friday
evening to Sunday morning</a>, and from <a href="wxdata0809/PNSLOX110408_1025PST.pdf" target="_blank">overnight
last night to 10:00 a.m. this morning</a>. The current Climate Prediction Center 6-10
day and 8-14 Precipitation Outlooks project below normal rainfall for Southern California.
In <a href="http://weatherclimatelink.blogspot.com/2008/10/dog-is-back-no-cookbooks.html" target="_blank">Atmospheric
Insights</a>, Ed Berry paints a scenario with an extended North Pacific Jet collapsing
into a strong western U.S. trough in the week 2-3 timeframe. We'll see!
</p>
<p>
<i>Update 11/1/08</i>. Did a trail run this morning in the Pt. Mugu State Park Area.
Over the course of 3+ hours watched 2-3 waves of convection <a href="http://www.photographyontherun.com/prun.asp?ifile=TStormOxnardPlain1000320d.jpg&amp;ic=Training convective cells marching northeast from the Santa Barbara Channel across the Oxnard Plain." target="_blank">march
northeast from the Santa Barbara Channel across the Oxnard Plain</a>. We were showered
on a few times, but were very happy to be east of these <a href="wxdata0809/wsicompradar_110108_2145animzb.gif" target="_blank">training
T-storms and heavy rain</a>. Here is a <a href="wxdata0809/PNSLOX110108_1137PDT.pdf" target="_blank">NWS
Public Information Statement</a> with some rainfall totals as of 11:00 a.m.
</p>
<p>
<span class="dropcap">M</span>ore information concerning Southern California weather
can be found using our <a href="weatherlinks.htm">WEATHER LINKS</a> page.
<br />
</p>
</td>
</tr>
</tbody>
</table>
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<br />
<hr />Southern California Weather Notes Copyright 2000-2017 Gary Valle. All Rights Reserved.climateGlobal Wind Oscillation (GWO)La NinaLos Angeles rainfallMultivariate ENSO Index (MEI)weatherprecipitation outlookhttp://www.sierraphotography.com/wxnotes/Trackback.aspx?guid=87e81dc4-e624-4f70-9ddc-e1a2c9dedba8http://www.sierraphotography.com/wxnotes/pingback.aspxhttp://www.sierraphotography.com/wxnotes/PermaLink,guid,87e81dc4-e624-4f70-9ddc-e1a2c9dedba8.aspxGary Valle

Drought Monitor Classification Change
Water Year Ending January 29, 2008

Sunday's storm added more rain to Southern California's
unexpectedly wet water year totals, and more snow to the Sierra snowpack. This rain
season western storms have reduced drought classifications by as much as three steps
in some areas of California and four in Arizona.

As of February 4, Downtown Los Angeles (USC- KCQT) has
recorded 12.13 inches of rain since July 1-- about 4.5 inches above normal for the
date. Here is an archived PDF of a NWS
Public Information Statement with some preliminary rainfall totals for Sunday's
storm.

Sierra snow
course measurements for February 1 are coming in and manual measurements are confirming
what automatic snow sensors have already reported -- that the Sierra snowpack is well
above normal for the date.

Will the wet western weather continue? The GFS and ECMWF
medium range models, and NCEP and PSD ensembles are forecasting a generally quiescent,
rain free period for Southern California over the next several days, and into the
extended period. Today's NWS 6-10 Day and 8-14 Day Precipitation Outlooks for Southern
California are indicating Below Normal precipitation.

However, there are suggestions (see Atmospheric
Insights) that sometime around February 15-20, the currently
active MJO may more or less phase with the GWO,
and amplify La Nina to produce a energetic, extended Pacific jet and west coast trough,
similar to what occurred around January 3, 2008. We'll see!

More information concerning Southern California weather
can be found using our WEATHER LINKS page.